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	$98.88	12.589%	$111.328	$111.33	$111.35	$111.30
Purchase #2	$173.50	6.223%	$184.2969	$184.30	$184.30	$184.30
Purchase #3	$107.32	12.492%	$120.7264	$120.73	$120.75	$120.70
Purchase #4	$198.41	5.144%	$208.6162	$208.62	$208.60	$208.60
Purchase #5	$147.25	12.569%	$165.7579	$165.76	$165.75	$165.80
Purchase #6	$165.67	3.350%	$171.2199	$171.22	$171.20	$171.20
Purchase #7	$127.78	5.534%	$134.8513	$134.85	$134.85	$134.90
7 purchase totals =	$1,018.81		$1,096.7966	$1,096.81	$1,096.80	$1,096.80