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	$142.78	6.351%	$151.848	$151.85	$151.85	$151.80
Purchase #2	$54.44	11.736%	$60.8291	$60.83	$60.85	$60.80
Purchase #3	$206.64	9.151%	$225.5496	$225.55	$225.55	$225.50
Purchase #4	$165.42	10.780%	$183.2523	$183.25	$183.25	$183.30
Purchase #5	$40.73	10.765%	$45.1146	$45.11	$45.10	$45.10
Purchase #6	$36.48	6.613%	$38.8924	$38.89	$38.90	$38.90
Purchase #7	$37.26	12.304%	$41.8445	$41.84	$41.85	$41.80
7 purchase totals =	$683.75		$747.3305	$747.32	$747.35	$747.20