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	$190.40	10.222%	$209.8627	$209.86	$209.85	$209.90
Purchase #2	$52.93	5.520%	$55.8517	$55.85	$55.85	$55.90
Purchase #3	$136.72	11.634%	$152.626	$152.63	$152.65	$152.60
Purchase #4	$65.36	4.515%	$68.311	$68.31	$68.30	$68.30
Purchase #5	$28.52	5.308%	$30.0338	$30.03	$30.05	$30.00
Purchase #6	$17.34	11.280%	$19.296	$19.30	$19.30	$19.30
Purchase #7	$243.54	9.168%	$265.8677	$265.87	$265.85	$265.90
7 purchase totals =	$734.81		$801.8489	$801.85	$801.85	$801.90