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	$45.47	13.360%	$51.5448	$51.54	$51.55	$51.50
Purchase #2	$248.82	13.496%	$282.4007	$282.40	$282.40	$282.40
Purchase #3	$47.33	11.277%	$52.6674	$52.67	$52.65	$52.70
Purchase #4	$202.27	10.146%	$222.7923	$222.79	$222.80	$222.80
Purchase #5	$205.55	8.662%	$223.3547	$223.35	$223.35	$223.40
Purchase #6	$129.86	12.696%	$146.347	$146.35	$146.35	$146.30
Purchase #7	$167.37	7.769%	$180.373	$180.37	$180.35	$180.40
7 purchase totals =	$1,046.67		$1,159.4799	$1,159.47	$1,159.45	$1,159.50