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	$118.31	10.474%	$130.7018	$130.70	$130.70	$130.70
Purchase #2	$84.43	12.842%	$95.2725	$95.27	$95.25	$95.30
Purchase #3	$67.90	6.232%	$72.1315	$72.13	$72.15	$72.10
Purchase #4	$124.32	9.788%	$136.4884	$136.49	$136.50	$136.50
Purchase #5	$58.31	11.301%	$64.8996	$64.90	$64.90	$64.90
Purchase #6	$151.66	8.856%	$165.091	$165.09	$165.10	$165.10
Purchase #7	$104.89	10.736%	$116.151	$116.15	$116.15	$116.20
7 purchase totals =	$709.82		$780.7358	$780.73	$780.75	$780.80