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	$210.90	10.859%	$233.8016	$233.80	$233.80	$233.80
Purchase #2	$170.66	10.438%	$188.4735	$188.47	$188.45	$188.50
Purchase #3	$192.36	4.216%	$200.4699	$200.47	$200.45	$200.50
Purchase #4	$111.31	13.111%	$125.9039	$125.90	$125.90	$125.90
Purchase #5	$222.68	9.173%	$243.1064	$243.11	$243.10	$243.10
Purchase #6	$196.89	8.300%	$213.2319	$213.23	$213.25	$213.20
Purchase #7	$168.27	9.427%	$184.1328	$184.13	$184.15	$184.10
7 purchase totals =	$1,273.07		$1,389.1200	$1,389.11	$1,389.10	$1,389.10