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	$42.96	5.255%	$45.2175	$45.22	$45.20	$45.20
Purchase #2	$138.47	8.462%	$150.1873	$150.19	$150.20	$150.20
Purchase #3	$39.57	10.229%	$43.6176	$43.62	$43.60	$43.60
Purchase #4	$174.65	10.820%	$193.5471	$193.55	$193.55	$193.50
Purchase #5	$209.81	10.173%	$231.154	$231.15	$231.15	$231.20
Purchase #6	$197.85	12.826%	$223.2262	$223.23	$223.25	$223.20
Purchase #7	$208.61	6.146%	$221.4312	$221.43	$221.45	$221.40
7 purchase totals =	$1,011.92		$1,108.3809	$1,108.39	$1,108.40	$1,108.30