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	$59.48	9.335%	$65.0325	$65.03	$65.05	$65.00
Purchase #2	$31.56	6.568%	$33.6329	$33.63	$33.65	$33.60
Purchase #3	$185.81	9.596%	$203.6403	$203.64	$203.65	$203.60
Purchase #4	$223.90	9.814%	$245.8735	$245.87	$245.85	$245.90
Purchase #5	$54.41	4.214%	$56.7028	$56.70	$56.70	$56.70
Purchase #6	$82.83	7.260%	$88.8435	$88.84	$88.85	$88.80
Purchase #7	$112.46	13.202%	$127.307	$127.31	$127.30	$127.30
7 purchase totals =	$750.45		$821.0325	$821.02	$821.05	$820.90