Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$181.59	5.721%	$191.9788	$191.98	$192.00	$192.00
Purchase #2	$209.63	12.813%	$236.4899	$236.49	$236.50	$236.50
Purchase #3	$227.28	10.208%	$250.4807	$250.48	$250.50	$250.50
Purchase #4	$127.54	6.841%	$136.265	$136.27	$136.25	$136.30
Purchase #5	$175.91	11.420%	$195.9989	$196.00	$196.00	$196.00
Purchase #6	$173.72	6.563%	$185.1212	$185.12	$185.10	$185.10
Purchase #7	$155.27	13.279%	$175.8883	$175.89	$175.90	$175.90
7 purchase totals =	$1,250.94		$1,372.2228	$1,372.23	$1,372.25	$1,372.30