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	$142.51	10.430%	$157.3738	$157.37	$157.35	$157.40
Purchase #2	$55.36	10.625%	$61.242	$61.24	$61.25	$61.20
Purchase #3	$151.81	9.293%	$165.9177	$165.92	$165.90	$165.90
Purchase #4	$11.84	12.602%	$13.3321	$13.33	$13.35	$13.30
Purchase #5	$130.38	9.631%	$142.9369	$142.94	$142.95	$142.90
Purchase #6	$114.83	11.299%	$127.8046	$127.80	$127.80	$127.80
Purchase #7	$172.32	7.435%	$185.132	$185.13	$185.15	$185.10
7 purchase totals =	$779.05		$853.7391	$853.73	$853.75	$853.60