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	$59.55	4.629%	$62.3066	$62.31	$62.30	$62.30
Purchase #2	$53.33	10.811%	$59.0955	$59.10	$59.10	$59.10
Purchase #3	$10.80	5.235%	$11.3654	$11.37	$11.35	$11.40
Purchase #4	$128.49	9.219%	$140.3355	$140.34	$140.35	$140.30
Purchase #5	$169.62	12.846%	$191.4094	$191.41	$191.40	$191.40
Purchase #6	$134.64	7.315%	$144.4889	$144.49	$144.50	$144.50
Purchase #7	$56.46	4.110%	$58.7805	$58.78	$58.80	$58.80
7 purchase totals =	$612.89		$667.7818	$667.80	$667.80	$667.80