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	$160.77	7.401%	$172.6686	$172.67	$172.65	$172.70
Purchase #2	$26.73	4.610%	$27.9623	$27.96	$27.95	$28.00
Purchase #3	$23.36	7.297%	$25.0646	$25.06	$25.05	$25.10
Purchase #4	$72.71	13.562%	$82.5709	$82.57	$82.55	$82.60
Purchase #5	$143.76	12.749%	$162.088	$162.09	$162.10	$162.10
Purchase #6	$167.83	8.204%	$181.5988	$181.60	$181.60	$181.60
Purchase #7	$102.31	13.764%	$116.3919	$116.39	$116.40	$116.40
7 purchase totals =	$697.47		$768.3451	$768.34	$768.30	$768.50