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	$237.47	10.311%	$261.9555	$261.96	$261.95	$262.00
Purchase #2	$80.48	11.717%	$89.9098	$89.91	$89.90	$89.90
Purchase #3	$106.63	13.488%	$121.0123	$121.01	$121.00	$121.00
Purchase #4	$239.88	12.199%	$269.143	$269.14	$269.15	$269.10
Purchase #5	$178.73	10.181%	$196.9265	$196.93	$196.95	$196.90
Purchase #6	$140.32	4.165%	$146.1643	$146.16	$146.15	$146.20
Purchase #7	$54.76	6.231%	$58.1721	$58.17	$58.15	$58.20
7 purchase totals =	$1,038.27		$1,143.2835	$1,143.28	$1,143.25	$1,143.30