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	$31.30	6.270%	$33.2625	$33.26	$33.25	$33.30
Purchase #2	$15.81	8.248%	$17.114	$17.11	$17.10	$17.10
Purchase #3	$55.59	9.358%	$60.7921	$60.79	$60.80	$60.80
Purchase #4	$96.54	9.256%	$105.4757	$105.48	$105.50	$105.50
Purchase #5	$67.41	3.349%	$69.6676	$69.67	$69.65	$69.70
Purchase #6	$137.55	10.609%	$152.1427	$152.14	$152.15	$152.10
Purchase #7	$85.36	4.370%	$89.0902	$89.09	$89.10	$89.10
7 purchase totals =	$489.56		$527.5448	$527.54	$527.55	$527.60