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	$104.69	6.559%	$111.5566	$111.56	$111.55	$111.60
Purchase #2	$79.78	6.380%	$84.87	$84.87	$84.85	$84.90
Purchase #3	$45.78	9.432%	$50.098	$50.10	$50.10	$50.10
Purchase #4	$154.75	13.472%	$175.5979	$175.60	$175.60	$175.60
Purchase #5	$177.51	8.781%	$193.0972	$193.10	$193.10	$193.10
Purchase #6	$53.74	6.705%	$57.3433	$57.34	$57.35	$57.30
Purchase #7	$78.34	9.209%	$85.5543	$85.55	$85.55	$85.60
7 purchase totals =	$694.59		$758.1173	$758.12	$758.10	$758.20