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	$113.44	8.791%	$123.4125	$123.41	$123.40	$123.40
Purchase #2	$172.57	12.142%	$193.5234	$193.52	$193.50	$193.50
Purchase #3	$164.98	10.466%	$182.2468	$182.25	$182.25	$182.20
Purchase #4	$22.86	11.736%	$25.5428	$25.54	$25.55	$25.50
Purchase #5	$143.84	7.860%	$155.1458	$155.15	$155.15	$155.10
Purchase #6	$202.36	10.404%	$223.4135	$223.41	$223.40	$223.40
Purchase #7	$135.41	12.310%	$152.079	$152.08	$152.10	$152.10
7 purchase totals =	$955.46		$1,055.3638	$1,055.36	$1,055.35	$1,055.20