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	$91.51	4.469%	$95.5996	$95.60	$95.60	$95.60
Purchase #2	$121.56	12.843%	$137.172	$137.17	$137.15	$137.20
Purchase #3	$71.91	13.199%	$81.4014	$81.40	$81.40	$81.40
Purchase #4	$82.33	9.273%	$89.9645	$89.96	$89.95	$90.00
Purchase #5	$200.74	13.629%	$228.0989	$228.10	$228.10	$228.10
Purchase #6	$193.30	6.368%	$205.6093	$205.61	$205.60	$205.60
Purchase #7	$56.91	8.542%	$61.7713	$61.77	$61.75	$61.80
7 purchase totals =	$818.26		$899.6170	$899.61	$899.55	$899.70