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	$67.32	5.240%	$70.8476	$70.85	$70.85	$70.80
Purchase #2	$137.41	10.306%	$151.5715	$151.57	$151.55	$151.60
Purchase #3	$214.85	6.273%	$228.3275	$228.33	$228.35	$228.30
Purchase #4	$98.31	3.471%	$101.7223	$101.72	$101.70	$101.70
Purchase #5	$250.94	5.730%	$265.3189	$265.32	$265.30	$265.30
Purchase #6	$6.44	7.504%	$6.9233	$6.92	$6.90	$6.90
Purchase #7	$145.34	4.746%	$152.2378	$152.24	$152.25	$152.20
7 purchase totals =	$920.61		$976.9489	$976.95	$976.90	$976.80