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	$119.60	10.306%	$131.926	$131.93	$131.95	$131.90
Purchase #2	$145.86	3.391%	$150.8061	$150.81	$150.80	$150.80
Purchase #3	$166.42	3.818%	$172.7739	$172.77	$172.75	$172.80
Purchase #4	$22.91	13.144%	$25.9213	$25.92	$25.90	$25.90
Purchase #5	$215.73	12.807%	$243.3585	$243.36	$243.35	$243.40
Purchase #6	$136.29	9.637%	$149.4243	$149.42	$149.40	$149.40
Purchase #7	$56.88	7.428%	$61.105	$61.11	$61.10	$61.10
7 purchase totals =	$863.69		$935.3151	$935.32	$935.25	$935.30