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	$63.32	4.743%	$66.3233	$66.32	$66.30	$66.30
Purchase #2	$146.86	6.411%	$156.2752	$156.28	$156.30	$156.30
Purchase #3	$31.65	4.424%	$33.0502	$33.05	$33.05	$33.10
Purchase #4	$21.84	6.402%	$23.2382	$23.24	$23.25	$23.20
Purchase #5	$62.36	12.598%	$70.2161	$70.22	$70.20	$70.20
Purchase #6	$37.72	7.384%	$40.5052	$40.51	$40.50	$40.50
Purchase #7	$44.32	4.566%	$46.3437	$46.34	$46.35	$46.30
7 purchase totals =	$408.07		$435.9519	$435.96	$435.95	$435.90