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	$220.33	4.228%	$229.6456	$229.65	$229.65	$229.60
Purchase #2	$169.94	13.749%	$193.3051	$193.31	$193.30	$193.30
Purchase #3	$97.56	6.451%	$103.8536	$103.85	$103.85	$103.90
Purchase #4	$154.62	9.648%	$169.5377	$169.54	$169.55	$169.50
Purchase #5	$119.85	6.621%	$127.7853	$127.79	$127.80	$127.80
Purchase #6	$223.41	11.232%	$248.5034	$248.50	$248.50	$248.50
Purchase #7	$56.56	4.853%	$59.3049	$59.30	$59.30	$59.30
7 purchase totals =	$1,042.27		$1,131.9356	$1,131.94	$1,131.95	$1,131.90