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	$233.99	12.652%	$263.5944	$263.59	$263.60	$263.60
Purchase #2	$35.96	8.315%	$38.9501	$38.95	$38.95	$39.00
Purchase #3	$223.34	9.821%	$245.2742	$245.27	$245.25	$245.30
Purchase #4	$135.26	9.500%	$148.1097	$148.11	$148.10	$148.10
Purchase #5	$53.84	10.440%	$59.4609	$59.46	$59.45	$59.50
Purchase #6	$199.97	13.628%	$227.2219	$227.22	$227.20	$227.20
Purchase #7	$40.50	7.515%	$43.5436	$43.54	$43.55	$43.50
7 purchase totals =	$922.86		$1,026.1548	$1,026.14	$1,026.10	$1,026.20