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	$39.69	8.543%	$43.0807	$43.08	$43.10	$43.10
Purchase #2	$10.53	7.869%	$11.3586	$11.36	$11.35	$11.40
Purchase #3	$106.35	5.818%	$112.5374	$112.54	$112.55	$112.50
Purchase #4	$245.41	8.353%	$265.9091	$265.91	$265.90	$265.90
Purchase #5	$200.46	11.724%	$223.9619	$223.96	$223.95	$224.00
Purchase #6	$93.45	12.718%	$105.335	$105.34	$105.35	$105.30
Purchase #7	$121.62	12.342%	$136.6303	$136.63	$136.65	$136.60
7 purchase totals =	$817.51		$898.8130	$898.82	$898.85	$898.80