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	$89.86	4.131%	$93.5721	$93.57	$93.55	$93.60
Purchase #2	$31.62	11.571%	$35.2788	$35.28	$35.30	$35.30
Purchase #3	$95.43	10.586%	$105.5322	$105.53	$105.55	$105.50
Purchase #4	$92.41	4.417%	$96.4917	$96.49	$96.50	$96.50
Purchase #5	$198.71	9.452%	$217.4921	$217.49	$217.50	$217.50
Purchase #6	$38.85	8.764%	$42.2548	$42.25	$42.25	$42.30
Purchase #7	$156.48	11.326%	$174.2029	$174.20	$174.20	$174.20
7 purchase totals =	$703.36		$764.8246	$764.81	$764.85	$764.90