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	$59.67	4.695%	$62.4715	$62.47	$62.45	$62.50
Purchase #2	$86.89	10.750%	$96.2307	$96.23	$96.25	$96.20
Purchase #3	$51.28	10.430%	$56.6285	$56.63	$56.65	$56.60
Purchase #4	$101.89	9.419%	$111.487	$111.49	$111.50	$111.50
Purchase #5	$47.33	6.771%	$50.5347	$50.53	$50.55	$50.50
Purchase #6	$201.69	10.220%	$222.3027	$222.30	$222.30	$222.30
Purchase #7	$31.71	5.379%	$33.4157	$33.42	$33.40	$33.40
7 purchase totals =	$580.46		$633.0708	$633.07	$633.10	$633.00