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	$209.96	4.291%	$218.9694	$218.97	$218.95	$219.00
Purchase #2	$56.79	3.524%	$58.7913	$58.79	$58.80	$58.80
Purchase #3	$85.89	12.765%	$96.8539	$96.85	$96.85	$96.90
Purchase #4	$37.46	9.748%	$41.1116	$41.11	$41.10	$41.10
Purchase #5	$216.78	10.789%	$240.1684	$240.17	$240.15	$240.20
Purchase #6	$62.93	13.833%	$71.6351	$71.64	$71.65	$71.60
Purchase #7	$43.39	5.718%	$45.871	$45.87	$45.85	$45.90
7 purchase totals =	$713.20		$773.4007	$773.40	$773.35	$773.50