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	$216.73	12.506%	$243.8343	$243.83	$243.85	$243.80
Purchase #2	$98.59	12.864%	$111.2726	$111.27	$111.25	$111.30
Purchase #3	$189.45	7.486%	$203.6322	$203.63	$203.65	$203.60
Purchase #4	$241.48	5.416%	$254.5586	$254.56	$254.55	$254.60
Purchase #5	$41.25	5.386%	$43.4717	$43.47	$43.45	$43.50
Purchase #6	$149.29	3.698%	$154.8107	$154.81	$154.80	$154.80
Purchase #7	$111.53	13.751%	$126.8665	$126.87	$126.85	$126.90
7 purchase totals =	$1,048.32		$1,138.4466	$1,138.44	$1,138.40	$1,138.50