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	$82.58	8.530%	$89.6241	$89.62	$89.60	$89.60
Purchase #2	$226.67	8.222%	$245.3068	$245.31	$245.30	$245.30
Purchase #3	$150.69	13.697%	$171.33	$171.33	$171.35	$171.30
Purchase #4	$240.52	6.694%	$256.6204	$256.62	$256.60	$256.60
Purchase #5	$86.96	12.412%	$97.7535	$97.75	$97.75	$97.80
Purchase #6	$19.68	5.775%	$20.8165	$20.82	$20.80	$20.80
Purchase #7	$157.53	6.557%	$167.8592	$167.86	$167.85	$167.90
7 purchase totals =	$964.63		$1,049.3105	$1,049.31	$1,049.25	$1,049.30