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	$78.96	7.745%	$85.0755	$85.08	$85.10	$85.10
Purchase #2	$47.86	11.507%	$53.3673	$53.37	$53.35	$53.40
Purchase #3	$140.33	8.249%	$151.9058	$151.91	$151.90	$151.90
Purchase #4	$54.72	7.455%	$58.7994	$58.80	$58.80	$58.80
Purchase #5	$183.65	11.336%	$204.4686	$204.47	$204.45	$204.50
Purchase #6	$148.77	6.270%	$158.0979	$158.10	$158.10	$158.10
Purchase #7	$83.37	7.654%	$89.7511	$89.75	$89.75	$89.80
7 purchase totals =	$737.66		$801.4656	$801.48	$801.45	$801.60