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	$83.54	6.677%	$89.118	$89.12	$89.10	$89.10
Purchase #2	$101.81	3.445%	$105.3174	$105.32	$105.30	$105.30
Purchase #3	$145.65	12.195%	$163.412	$163.41	$163.40	$163.40
Purchase #4	$160.75	13.240%	$182.0333	$182.03	$182.05	$182.00
Purchase #5	$235.58	9.343%	$257.5902	$257.59	$257.60	$257.60
Purchase #6	$147.31	12.504%	$165.7296	$165.73	$165.75	$165.70
Purchase #7	$151.30	8.655%	$164.395	$164.40	$164.40	$164.40
7 purchase totals =	$1,025.94		$1,127.5955	$1,127.60	$1,127.60	$1,127.50