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	$28.84	11.195%	$32.0686	$32.07	$32.05	$32.10
Purchase #2	$237.81	4.730%	$249.0584	$249.06	$249.05	$249.10
Purchase #3	$91.28	7.521%	$98.1452	$98.15	$98.15	$98.10
Purchase #4	$229.64	13.144%	$259.8239	$259.82	$259.80	$259.80
Purchase #5	$248.93	8.169%	$269.2651	$269.27	$269.25	$269.30
Purchase #6	$13.52	10.148%	$14.892	$14.89	$14.90	$14.90
Purchase #7	$235.42	6.498%	$250.7176	$250.72	$250.70	$250.70
7 purchase totals =	$1,085.44		$1,173.9708	$1,173.98	$1,173.90	$1,174.00