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	$41.51	9.732%	$45.5498	$45.55	$45.55	$45.50
Purchase #2	$33.53	4.423%	$35.013	$35.01	$35.00	$35.00
Purchase #3	$67.96	3.472%	$70.3196	$70.32	$70.30	$70.30
Purchase #4	$138.85	6.481%	$147.8489	$147.85	$147.85	$147.80
Purchase #5	$119.79	8.261%	$129.6859	$129.69	$129.70	$129.70
Purchase #6	$227.33	12.200%	$255.0643	$255.06	$255.05	$255.10
Purchase #7	$28.39	9.589%	$31.1123	$31.11	$31.10	$31.10
7 purchase totals =	$657.36		$714.5938	$714.59	$714.55	$714.50