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	$165.28	3.548%	$171.1441	$171.14	$171.15	$171.10
Purchase #2	$120.94	13.506%	$137.2742	$137.27	$137.25	$137.30
Purchase #3	$147.65	3.396%	$152.6642	$152.66	$152.65	$152.70
Purchase #4	$175.49	5.606%	$185.328	$185.33	$185.35	$185.30
Purchase #5	$100.56	8.812%	$109.4213	$109.42	$109.40	$109.40
Purchase #6	$89.88	6.370%	$95.6054	$95.61	$95.60	$95.60
Purchase #7	$194.42	7.562%	$209.122	$209.12	$209.10	$209.10
7 purchase totals =	$994.22		$1,060.5592	$1,060.55	$1,060.50	$1,060.50