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	$90.66	4.630%	$94.8576	$94.86	$94.85	$94.90
Purchase #2	$151.59	10.213%	$167.0719	$167.07	$167.05	$167.10
Purchase #3	$89.66	4.331%	$93.5432	$93.54	$93.55	$93.50
Purchase #4	$222.88	9.460%	$243.9644	$243.96	$243.95	$244.00
Purchase #5	$109.36	13.136%	$123.7255	$123.73	$123.75	$123.70
Purchase #6	$23.83	7.597%	$25.6404	$25.64	$25.65	$25.60
Purchase #7	$130.94	9.144%	$142.9132	$142.91	$142.90	$142.90
7 purchase totals =	$818.92		$891.7162	$891.71	$891.70	$891.70