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	$43.63	3.693%	$45.2413	$45.24	$45.25	$45.20
Purchase #2	$206.41	6.236%	$219.2817	$219.28	$219.30	$219.30
Purchase #3	$119.39	7.486%	$128.3275	$128.33	$128.35	$128.30
Purchase #4	$38.76	12.729%	$43.6938	$43.69	$43.70	$43.70
Purchase #5	$10.87	13.835%	$12.3739	$12.37	$12.35	$12.40
Purchase #6	$98.68	10.760%	$109.298	$109.30	$109.30	$109.30
Purchase #7	$61.83	6.627%	$65.9275	$65.93	$65.95	$65.90
7 purchase totals =	$579.57		$624.1437	$624.14	$624.20	$624.10