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	$114.59	7.341%	$123.0021	$123.00	$123.00	$123.00
Purchase #2	$25.87	5.670%	$27.3368	$27.34	$27.35	$27.30
Purchase #3	$210.97	4.155%	$219.7358	$219.74	$219.75	$219.70
Purchase #4	$120.30	5.502%	$126.9189	$126.92	$126.90	$126.90
Purchase #5	$136.94	13.465%	$155.379	$155.38	$155.40	$155.40
Purchase #6	$40.59	11.291%	$45.173	$45.17	$45.15	$45.20
Purchase #7	$239.33	10.862%	$265.326	$265.33	$265.35	$265.30
7 purchase totals =	$888.59		$962.8716	$962.88	$962.90	$962.80