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	$42.33	7.282%	$45.4125	$45.41	$45.40	$45.40
Purchase #2	$7.82	7.488%	$8.4056	$8.41	$8.40	$8.40
Purchase #3	$78.28	6.521%	$83.3846	$83.38	$83.40	$83.40
Purchase #4	$239.93	7.260%	$257.3489	$257.35	$257.35	$257.30
Purchase #5	$85.41	13.443%	$96.8917	$96.89	$96.90	$96.90
Purchase #6	$209.76	4.723%	$219.667	$219.67	$219.65	$219.70
Purchase #7	$41.52	4.431%	$43.3598	$43.36	$43.35	$43.40
7 purchase totals =	$705.05		$754.4701	$754.47	$754.45	$754.50