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	$83.82	6.252%	$89.0604	$89.06	$89.05	$89.10
Purchase #2	$84.38	12.226%	$94.6963	$94.70	$94.70	$94.70
Purchase #3	$48.76	11.319%	$54.2791	$54.28	$54.30	$54.30
Purchase #4	$167.53	4.118%	$174.4289	$174.43	$174.45	$174.40
Purchase #5	$124.30	8.483%	$134.8444	$134.84	$134.85	$134.80
Purchase #6	$90.46	6.384%	$96.235	$96.24	$96.25	$96.20
Purchase #7	$37.32	13.865%	$42.4944	$42.49	$42.50	$42.50
7 purchase totals =	$636.57		$686.0385	$686.04	$686.10	$686.00