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	$86.70	4.735%	$90.8052	$90.81	$90.80	$90.80
Purchase #2	$170.63	6.651%	$181.9786	$181.98	$182.00	$182.00
Purchase #3	$195.56	8.289%	$211.77	$211.77	$211.75	$211.80
Purchase #4	$142.59	11.506%	$158.9964	$159.00	$159.00	$159.00
Purchase #5	$55.48	7.527%	$59.656	$59.66	$59.65	$59.70
Purchase #6	$240.69	6.190%	$255.5887	$255.59	$255.60	$255.60
Purchase #7	$13.31	10.644%	$14.7267	$14.73	$14.75	$14.70
7 purchase totals =	$904.96		$973.5216	$973.54	$973.55	$973.60