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	$210.85	13.116%	$238.5051	$238.51	$238.50	$238.50
Purchase #2	$109.34	9.298%	$119.5064	$119.51	$119.50	$119.50
Purchase #3	$189.63	11.263%	$210.988	$210.99	$211.00	$211.00
Purchase #4	$72.90	10.760%	$80.744	$80.74	$80.75	$80.70
Purchase #5	$196.98	7.662%	$212.0726	$212.07	$212.05	$212.10
Purchase #6	$160.47	7.740%	$172.8904	$172.89	$172.90	$172.90
Purchase #7	$125.68	4.548%	$131.3959	$131.40	$131.40	$131.40
7 purchase totals =	$1,065.85		$1,166.1024	$1,166.11	$1,166.10	$1,166.10