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	$186.30	5.390%	$196.3416	$196.34	$196.35	$196.30
Purchase #2	$189.63	11.395%	$211.2383	$211.24	$211.25	$211.20
Purchase #3	$142.54	6.842%	$152.2926	$152.29	$152.30	$152.30
Purchase #4	$96.29	7.705%	$103.7091	$103.71	$103.70	$103.70
Purchase #5	$36.91	10.473%	$40.7756	$40.78	$40.80	$40.80
Purchase #6	$244.65	7.234%	$262.348	$262.35	$262.35	$262.30
Purchase #7	$157.28	5.812%	$166.4211	$166.42	$166.40	$166.40
7 purchase totals =	$1,053.60		$1,133.1263	$1,133.13	$1,133.15	$1,133.00