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	$56.73	7.219%	$60.8253	$60.83	$60.85	$60.80
Purchase #2	$132.60	9.420%	$145.0909	$145.09	$145.10	$145.10
Purchase #3	$151.76	5.784%	$160.5378	$160.54	$160.55	$160.50
Purchase #4	$159.33	12.256%	$178.8575	$178.86	$178.85	$178.90
Purchase #5	$150.27	11.211%	$167.1168	$167.12	$167.10	$167.10
Purchase #6	$141.55	11.689%	$158.0958	$158.10	$158.10	$158.10
Purchase #7	$145.31	4.822%	$152.3168	$152.32	$152.30	$152.30
7 purchase totals =	$937.55		$1,022.8409	$1,022.86	$1,022.85	$1,022.80