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	$144.50	5.274%	$152.1209	$152.12	$152.10	$152.10
Purchase #2	$54.36	12.222%	$61.0039	$61.00	$61.00	$61.00
Purchase #3	$52.83	9.688%	$57.9482	$57.95	$57.95	$57.90
Purchase #4	$78.28	5.217%	$82.3639	$82.36	$82.35	$82.40
Purchase #5	$190.74	3.110%	$196.672	$196.67	$196.65	$196.70
Purchase #6	$19.63	4.130%	$20.4407	$20.44	$20.45	$20.40
Purchase #7	$157.65	8.728%	$171.4097	$171.41	$171.40	$171.40
7 purchase totals =	$697.99		$741.9593	$741.95	$741.90	$741.90