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	$96.90	4.138%	$100.9097	$100.91	$100.90	$100.90
Purchase #2	$241.79	3.778%	$250.9248	$250.92	$250.90	$250.90
Purchase #3	$139.89	3.701%	$145.0673	$145.07	$145.05	$145.10
Purchase #4	$66.44	7.788%	$71.6143	$71.61	$71.60	$71.60
Purchase #5	$81.87	13.738%	$93.1173	$93.12	$93.10	$93.10
Purchase #6	$210.97	6.347%	$224.3603	$224.36	$224.35	$224.40
Purchase #7	$207.95	5.710%	$219.8239	$219.82	$219.80	$219.80
7 purchase totals =	$1,045.81		$1,105.8176	$1,105.81	$1,105.70	$1,105.80