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	$142.27	4.820%	$149.1274	$149.13	$149.15	$149.10
Purchase #2	$132.36	7.468%	$142.2446	$142.24	$142.25	$142.20
Purchase #3	$93.36	3.727%	$96.8395	$96.84	$96.85	$96.80
Purchase #4	$137.89	9.811%	$151.4184	$151.42	$151.40	$151.40
Purchase #5	$20.78	4.385%	$21.6912	$21.69	$21.70	$21.70
Purchase #6	$95.55	11.830%	$106.8536	$106.85	$106.85	$106.90
Purchase #7	$94.49	5.192%	$99.3959	$99.40	$99.40	$99.40
7 purchase totals =	$716.70		$767.5706	$767.57	$767.60	$767.50