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	$66.62	6.769%	$71.1295	$71.13	$71.15	$71.10
Purchase #2	$26.78	6.752%	$28.5882	$28.59	$28.60	$28.60
Purchase #3	$243.59	7.208%	$261.148	$261.15	$261.15	$261.10
Purchase #4	$246.91	11.717%	$275.8404	$275.84	$275.85	$275.80
Purchase #5	$144.78	13.496%	$164.3195	$164.32	$164.30	$164.30
Purchase #6	$79.38	6.238%	$84.3317	$84.33	$84.35	$84.30
Purchase #7	$161.89	3.527%	$167.5999	$167.60	$167.60	$167.60
7 purchase totals =	$969.95		$1,052.9572	$1,052.96	$1,053.00	$1,052.80