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	$60.96	11.284%	$67.8387	$67.84	$67.85	$67.80
Purchase #2	$229.72	3.762%	$238.3621	$238.36	$238.35	$238.40
Purchase #3	$223.67	13.136%	$253.0513	$253.05	$253.05	$253.10
Purchase #4	$81.63	10.119%	$89.8901	$89.89	$89.90	$89.90
Purchase #5	$122.34	9.793%	$134.3208	$134.32	$134.30	$134.30
Purchase #6	$115.59	9.691%	$126.7918	$126.79	$126.80	$126.80
Purchase #7	$94.43	7.837%	$101.8305	$101.83	$101.85	$101.80
7 purchase totals =	$928.34		$1,012.0853	$1,012.08	$1,012.10	$1,012.10