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	$112.84	10.165%	$124.3102	$124.31	$124.30	$124.30
Purchase #2	$239.66	10.198%	$264.1005	$264.10	$264.10	$264.10
Purchase #3	$95.79	4.152%	$99.7672	$99.77	$99.75	$99.80
Purchase #4	$96.62	4.383%	$100.8549	$100.85	$100.85	$100.90
Purchase #5	$108.31	13.795%	$123.2514	$123.25	$123.25	$123.30
Purchase #6	$38.77	6.223%	$41.1827	$41.18	$41.20	$41.20
Purchase #7	$136.78	8.692%	$148.6689	$148.67	$148.65	$148.70
7 purchase totals =	$828.77		$902.1358	$902.13	$902.10	$902.30