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	$60.35	8.772%	$65.6439	$65.64	$65.65	$65.60
Purchase #2	$190.72	13.698%	$216.8448	$216.84	$216.85	$216.80
Purchase #3	$207.57	8.595%	$225.4106	$225.41	$225.40	$225.40
Purchase #4	$82.46	8.315%	$89.3165	$89.32	$89.30	$89.30
Purchase #5	$199.59	9.793%	$219.1358	$219.14	$219.15	$219.10
Purchase #6	$216.96	8.276%	$234.9156	$234.92	$234.90	$234.90
Purchase #7	$112.89	8.592%	$122.5895	$122.59	$122.60	$122.60
7 purchase totals =	$1,070.54		$1,173.8567	$1,173.86	$1,173.85	$1,173.70