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	$129.95	13.588%	$147.6076	$147.61	$147.60	$147.60
Purchase #2	$166.87	9.104%	$182.0618	$182.06	$182.05	$182.10
Purchase #3	$32.32	9.723%	$35.4625	$35.46	$35.45	$35.50
Purchase #4	$73.89	7.609%	$79.5123	$79.51	$79.50	$79.50
Purchase #5	$139.53	9.580%	$152.897	$152.90	$152.90	$152.90
Purchase #6	$85.41	10.438%	$94.3251	$94.33	$94.35	$94.30
Purchase #7	$48.94	13.354%	$55.4754	$55.48	$55.50	$55.50
7 purchase totals =	$676.91		$747.3417	$747.35	$747.35	$747.40