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	$173.90	5.415%	$183.3167	$183.32	$183.30	$183.30
Purchase #2	$238.74	7.325%	$256.2277	$256.23	$256.25	$256.20
Purchase #3	$186.67	3.400%	$193.0168	$193.02	$193.00	$193.00
Purchase #4	$145.92	7.172%	$156.3854	$156.39	$156.40	$156.40
Purchase #5	$124.46	3.430%	$128.729	$128.73	$128.75	$128.70
Purchase #6	$24.89	9.505%	$27.2558	$27.26	$27.25	$27.30
Purchase #7	$63.90	11.787%	$71.4319	$71.43	$71.45	$71.40
7 purchase totals =	$958.48		$1,016.3633	$1,016.38	$1,016.40	$1,016.30