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	$144.76	7.670%	$155.8631	$155.86	$155.85	$155.90
Purchase #2	$53.33	13.133%	$60.3338	$60.33	$60.35	$60.30
Purchase #3	$233.69	10.811%	$258.9542	$258.95	$258.95	$259.00
Purchase #4	$165.43	3.803%	$171.7213	$171.72	$171.70	$171.70
Purchase #5	$62.61	12.404%	$70.3761	$70.38	$70.40	$70.40
Purchase #6	$84.60	10.667%	$93.6243	$93.62	$93.60	$93.60
Purchase #7	$79.62	12.479%	$89.5558	$89.56	$89.55	$89.60
7 purchase totals =	$824.04		$900.4286	$900.42	$900.40	$900.50