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	$197.48	6.760%	$210.8296	$210.83	$210.85	$210.80
Purchase #2	$30.99	8.798%	$33.7165	$33.72	$33.70	$33.70
Purchase #3	$44.94	8.784%	$48.8875	$48.89	$48.90	$48.90
Purchase #4	$179.62	11.497%	$200.2709	$200.27	$200.25	$200.30
Purchase #5	$55.50	12.303%	$62.3282	$62.33	$62.35	$62.30
Purchase #6	$139.39	9.722%	$152.9415	$152.94	$152.95	$152.90
Purchase #7	$200.97	10.134%	$221.3363	$221.34	$221.35	$221.30
7 purchase totals =	$848.89		$930.3105	$930.32	$930.35	$930.20