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	$88.98	10.436%	$98.266	$98.27	$98.25	$98.30
Purchase #2	$70.44	11.842%	$78.7815	$78.78	$78.80	$78.80
Purchase #3	$232.39	10.542%	$256.8886	$256.89	$256.90	$256.90
Purchase #4	$139.28	3.203%	$143.7411	$143.74	$143.75	$143.70
Purchase #5	$62.66	5.802%	$66.2955	$66.30	$66.30	$66.30
Purchase #6	$222.51	9.295%	$243.1923	$243.19	$243.20	$243.20
Purchase #7	$160.85	3.279%	$166.1243	$166.12	$166.10	$166.10
7 purchase totals =	$977.11		$1,053.2893	$1,053.29	$1,053.30	$1,053.30