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	$113.53	3.435%	$117.4298	$117.43	$117.45	$117.40
Purchase #2	$130.81	3.115%	$134.8847	$134.88	$134.90	$134.90
Purchase #3	$78.84	3.325%	$81.4614	$81.46	$81.45	$81.50
Purchase #4	$57.33	7.377%	$61.5592	$61.56	$61.55	$61.60
Purchase #5	$85.30	6.215%	$90.6014	$90.60	$90.60	$90.60
Purchase #6	$54.63	5.424%	$57.5931	$57.59	$57.60	$57.60
Purchase #7	$242.42	6.506%	$258.1918	$258.19	$258.20	$258.20
7 purchase totals =	$762.86		$801.7214	$801.71	$801.75	$801.80