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	$67.43	4.277%	$70.314	$70.31	$70.30	$70.30
Purchase #2	$179.39	6.646%	$191.3123	$191.31	$191.30	$191.30
Purchase #3	$102.79	9.840%	$112.9045	$112.90	$112.90	$112.90
Purchase #4	$228.26	6.680%	$243.5078	$243.51	$243.50	$243.50
Purchase #5	$230.88	4.519%	$241.3135	$241.31	$241.30	$241.30
Purchase #6	$116.80	9.513%	$127.9112	$127.91	$127.90	$127.90
Purchase #7	$121.31	4.636%	$126.9339	$126.93	$126.95	$126.90
7 purchase totals =	$1,046.86		$1,114.1972	$1,114.18	$1,114.15	$1,114.10