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	$179.90	3.169%	$185.601	$185.60	$185.60	$185.60
Purchase #2	$235.61	10.821%	$261.1054	$261.11	$261.10	$261.10
Purchase #3	$86.58	12.718%	$97.5912	$97.59	$97.60	$97.60
Purchase #4	$16.68	13.340%	$18.9051	$18.91	$18.90	$18.90
Purchase #5	$243.60	10.299%	$268.6884	$268.69	$268.70	$268.70
Purchase #6	$138.59	3.462%	$143.388	$143.39	$143.40	$143.40
Purchase #7	$73.49	8.265%	$79.5639	$79.56	$79.55	$79.60
7 purchase totals =	$974.45		$1,054.8430	$1,054.85	$1,054.85	$1,054.90