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	$97.81	13.700%	$111.21	$111.21	$111.20	$111.20
Purchase #2	$154.90	4.783%	$162.3089	$162.31	$162.30	$162.30
Purchase #3	$61.98	8.742%	$67.3983	$67.40	$67.40	$67.40
Purchase #4	$44.62	11.812%	$49.8905	$49.89	$49.90	$49.90
Purchase #5	$42.43	3.503%	$43.9163	$43.92	$43.90	$43.90
Purchase #6	$92.76	13.809%	$105.5692	$105.57	$105.55	$105.60
Purchase #7	$21.58	5.417%	$22.749	$22.75	$22.75	$22.70
7 purchase totals =	$516.08		$563.0422	$563.05	$563.00	$563.00