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	$109.89	4.775%	$115.1372	$115.14	$115.15	$115.10
Purchase #2	$100.84	10.168%	$111.0934	$111.09	$111.10	$111.10
Purchase #3	$131.45	13.660%	$149.4061	$149.41	$149.40	$149.40
Purchase #4	$243.57	4.639%	$254.8692	$254.87	$254.85	$254.90
Purchase #5	$67.67	6.610%	$72.143	$72.14	$72.15	$72.10
Purchase #6	$182.61	8.660%	$198.424	$198.42	$198.40	$198.40
Purchase #7	$238.39	10.714%	$263.9311	$263.93	$263.95	$263.90
7 purchase totals =	$1,074.42		$1,165.0040	$1,165.00	$1,165.00	$1,164.90