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	$67.91	5.213%	$71.4501	$71.45	$71.45	$71.50
Purchase #2	$33.74	5.771%	$35.6871	$35.69	$35.70	$35.70
Purchase #3	$158.28	6.781%	$169.013	$169.01	$169.00	$169.00
Purchase #4	$189.56	13.107%	$214.4056	$214.41	$214.40	$214.40
Purchase #5	$147.63	12.404%	$165.942	$165.94	$165.95	$165.90
Purchase #6	$39.64	8.819%	$43.1359	$43.14	$43.15	$43.10
Purchase #7	$33.46	6.141%	$35.5148	$35.51	$35.50	$35.50
7 purchase totals =	$670.22		$735.1485	$735.15	$735.15	$735.10