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	$156.84	6.638%	$167.251	$167.25	$167.25	$167.30
Purchase #2	$201.79	4.426%	$210.7212	$210.72	$210.70	$210.70
Purchase #3	$9.94	11.806%	$11.1135	$11.11	$11.10	$11.10
Purchase #4	$86.84	13.345%	$98.4288	$98.43	$98.45	$98.40
Purchase #5	$128.40	6.191%	$136.3492	$136.35	$136.35	$136.30
Purchase #6	$37.72	12.668%	$42.4984	$42.50	$42.50	$42.50
Purchase #7	$142.71	11.499%	$159.1202	$159.12	$159.10	$159.10
7 purchase totals =	$764.24		$825.4823	$825.48	$825.45	$825.40