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	$48.59	10.666%	$53.7726	$53.77	$53.75	$53.80
Purchase #2	$166.71	11.220%	$185.4149	$185.41	$185.40	$185.40
Purchase #3	$143.93	12.707%	$162.2192	$162.22	$162.20	$162.20
Purchase #4	$208.79	11.557%	$232.9199	$232.92	$232.90	$232.90
Purchase #5	$214.89	5.627%	$226.9819	$226.98	$227.00	$227.00
Purchase #6	$102.43	13.387%	$116.1423	$116.14	$116.15	$116.10
Purchase #7	$96.33	7.779%	$103.8235	$103.82	$103.80	$103.80
7 purchase totals =	$981.67		$1,081.2743	$1,081.26	$1,081.20	$1,081.20