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	$163.42	9.811%	$179.4531	$179.45	$179.45	$179.50
Purchase #2	$70.70	11.114%	$78.5576	$78.56	$78.55	$78.60
Purchase #3	$62.88	9.140%	$68.6272	$68.63	$68.65	$68.60
Purchase #4	$160.86	9.516%	$176.1674	$176.17	$176.15	$176.20
Purchase #5	$48.91	11.495%	$54.5322	$54.53	$54.55	$54.50
Purchase #6	$212.89	4.769%	$223.0427	$223.04	$223.05	$223.00
Purchase #7	$247.92	4.796%	$259.8102	$259.81	$259.80	$259.80
7 purchase totals =	$967.58		$1,040.1904	$1,040.19	$1,040.20	$1,040.20