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	$117.33	8.138%	$126.8783	$126.88	$126.90	$126.90
Purchase #2	$197.91	3.635%	$205.104	$205.10	$205.10	$205.10
Purchase #3	$146.71	8.478%	$159.1481	$159.15	$159.15	$159.10
Purchase #4	$216.61	7.646%	$233.172	$233.17	$233.15	$233.20
Purchase #5	$100.91	8.502%	$109.4894	$109.49	$109.50	$109.50
Purchase #6	$165.35	12.143%	$185.4285	$185.43	$185.45	$185.40
Purchase #7	$148.32	13.675%	$168.6028	$168.60	$168.60	$168.60
7 purchase totals =	$1,093.14		$1,187.8231	$1,187.82	$1,187.85	$1,187.80