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	$197.98	9.330%	$216.4515	$216.45	$216.45	$216.50
Purchase #2	$146.84	10.597%	$162.4006	$162.40	$162.40	$162.40
Purchase #3	$21.41	6.304%	$22.7597	$22.76	$22.75	$22.80
Purchase #4	$148.30	7.106%	$158.8382	$158.84	$158.85	$158.80
Purchase #5	$82.29	12.636%	$92.6882	$92.69	$92.70	$92.70
Purchase #6	$28.70	12.241%	$32.2132	$32.21	$32.20	$32.20
Purchase #7	$83.92	6.142%	$89.0744	$89.07	$89.05	$89.10
7 purchase totals =	$709.44		$774.4258	$774.42	$774.40	$774.50