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	$65.29	3.110%	$67.3205	$67.32	$67.30	$67.30
Purchase #2	$196.88	12.805%	$222.0905	$222.09	$222.10	$222.10
Purchase #3	$247.95	13.593%	$281.6538	$281.65	$281.65	$281.70
Purchase #4	$215.94	6.171%	$229.2657	$229.27	$229.25	$229.30
Purchase #5	$176.54	12.871%	$199.2625	$199.26	$199.25	$199.30
Purchase #6	$233.50	6.869%	$249.5391	$249.54	$249.55	$249.50
Purchase #7	$13.79	3.543%	$14.2786	$14.28	$14.30	$14.30
7 purchase totals =	$1,149.89		$1,263.4107	$1,263.41	$1,263.40	$1,263.50