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	$103.74	4.839%	$108.76	$108.76	$108.75	$108.80
Purchase #2	$139.94	5.234%	$147.2645	$147.26	$147.25	$147.30
Purchase #3	$86.74	6.430%	$92.3174	$92.32	$92.30	$92.30
Purchase #4	$50.37	9.398%	$55.1038	$55.10	$55.10	$55.10
Purchase #5	$175.51	7.350%	$188.41	$188.41	$188.40	$188.40
Purchase #6	$215.52	10.445%	$238.0311	$238.03	$238.05	$238.00
Purchase #7	$33.89	5.403%	$35.7211	$35.72	$35.70	$35.70
7 purchase totals =	$805.71		$865.6079	$865.60	$865.55	$865.60