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	$152.56	7.159%	$163.4818	$163.48	$163.50	$163.50
Purchase #2	$94.46	5.399%	$99.5599	$99.56	$99.55	$99.60
Purchase #3	$52.48	5.520%	$55.3769	$55.38	$55.40	$55.40
Purchase #4	$138.81	12.241%	$155.8017	$155.80	$155.80	$155.80
Purchase #5	$75.67	12.558%	$85.1726	$85.17	$85.15	$85.20
Purchase #6	$124.57	7.271%	$133.6275	$133.63	$133.65	$133.60
Purchase #7	$28.63	13.186%	$32.4052	$32.41	$32.40	$32.40
7 purchase totals =	$667.18		$725.4256	$725.43	$725.45	$725.50