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	$234.63	10.604%	$259.5102	$259.51	$259.50	$259.50
Purchase #2	$57.82	6.576%	$61.6222	$61.62	$61.60	$61.60
Purchase #3	$209.79	6.647%	$223.7347	$223.73	$223.75	$223.70
Purchase #4	$145.69	4.295%	$151.9474	$151.95	$151.95	$151.90
Purchase #5	$137.67	13.512%	$156.272	$156.27	$156.25	$156.30
Purchase #6	$106.46	5.754%	$112.5857	$112.59	$112.60	$112.60
Purchase #7	$137.58	5.482%	$145.1221	$145.12	$145.10	$145.10
7 purchase totals =	$1,029.64		$1,110.7943	$1,110.79	$1,110.75	$1,110.70