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	$79.33	11.307%	$88.2998	$88.30	$88.30	$88.30
Purchase #2	$123.88	8.675%	$134.6266	$134.63	$134.65	$134.60
Purchase #3	$117.31	11.402%	$130.6857	$130.69	$130.70	$130.70
Purchase #4	$59.59	3.209%	$61.5022	$61.50	$61.50	$61.50
Purchase #5	$189.65	3.413%	$196.1228	$196.12	$196.10	$196.10
Purchase #6	$92.28	4.475%	$96.4095	$96.41	$96.40	$96.40
Purchase #7	$25.72	13.364%	$29.1572	$29.16	$29.15	$29.20
7 purchase totals =	$687.76		$736.8038	$736.81	$736.80	$736.80