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	$118.48	11.220%	$131.7735	$131.77	$131.75	$131.80
Purchase #2	$58.63	12.122%	$65.7371	$65.74	$65.75	$65.70
Purchase #3	$53.61	3.665%	$55.5748	$55.57	$55.55	$55.60
Purchase #4	$31.55	4.397%	$32.9373	$32.94	$32.95	$32.90
Purchase #5	$172.80	6.600%	$184.2048	$184.20	$184.20	$184.20
Purchase #6	$89.43	3.249%	$92.3356	$92.34	$92.35	$92.30
Purchase #7	$122.77	11.362%	$136.7191	$136.72	$136.70	$136.70
7 purchase totals =	$647.27		$699.2822	$699.28	$699.25	$699.20