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	$35.60	7.711%	$38.3451	$38.35	$38.35	$38.30
Purchase #2	$170.30	3.220%	$175.7837	$175.78	$175.80	$175.80
Purchase #3	$127.70	10.203%	$140.7292	$140.73	$140.75	$140.70
Purchase #4	$91.97	3.769%	$95.4363	$95.44	$95.45	$95.40
Purchase #5	$18.89	13.238%	$21.3907	$21.39	$21.40	$21.40
Purchase #6	$54.39	9.497%	$59.5554	$59.56	$59.55	$59.60
Purchase #7	$235.60	7.411%	$253.0603	$253.06	$253.05	$253.10
7 purchase totals =	$734.45		$784.3007	$784.31	$784.35	$784.30