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	$43.55	5.407%	$45.9047	$45.90	$45.90	$45.90
Purchase #2	$13.67	12.525%	$15.3822	$15.38	$15.40	$15.40
Purchase #3	$93.25	10.740%	$103.2651	$103.27	$103.25	$103.30
Purchase #4	$183.86	7.107%	$196.9269	$196.93	$196.95	$196.90
Purchase #5	$149.95	13.148%	$169.6654	$169.67	$169.65	$169.70
Purchase #6	$37.65	10.339%	$41.5426	$41.54	$41.55	$41.50
Purchase #7	$209.57	12.386%	$235.5273	$235.53	$235.55	$235.50
7 purchase totals =	$731.50		$808.2142	$808.22	$808.25	$808.20