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	$247.74	11.231%	$275.5637	$275.56	$275.55	$275.60
Purchase #2	$230.76	10.449%	$254.8721	$254.87	$254.85	$254.90
Purchase #3	$246.46	3.738%	$255.6727	$255.67	$255.65	$255.70
Purchase #4	$185.78	6.840%	$198.4874	$198.49	$198.50	$198.50
Purchase #5	$35.42	9.399%	$38.7491	$38.75	$38.75	$38.70
Purchase #6	$10.65	9.782%	$11.6918	$11.69	$11.70	$11.70
Purchase #7	$184.41	6.327%	$196.0776	$196.08	$196.10	$196.10
7 purchase totals =	$1,141.22		$1,231.1144	$1,231.11	$1,231.10	$1,231.20