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	$121.73	5.823%	$128.8183	$128.82	$128.80	$128.80
Purchase #2	$188.76	11.134%	$209.7765	$209.78	$209.80	$209.80
Purchase #3	$45.85	3.732%	$47.5611	$47.56	$47.55	$47.60
Purchase #4	$21.76	12.255%	$24.4267	$24.43	$24.45	$24.40
Purchase #5	$38.37	3.685%	$39.7839	$39.78	$39.80	$39.80
Purchase #6	$105.87	3.554%	$109.6326	$109.63	$109.65	$109.60
Purchase #7	$197.41	11.178%	$219.4765	$219.48	$219.50	$219.50
7 purchase totals =	$719.75		$779.4756	$779.48	$779.55	$779.50