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	$159.36	5.573%	$168.2411	$168.24	$168.25	$168.20
Purchase #2	$168.30	7.580%	$181.0571	$181.06	$181.05	$181.10
Purchase #3	$136.50	13.758%	$155.2797	$155.28	$155.30	$155.30
Purchase #4	$177.37	5.377%	$186.9072	$186.91	$186.90	$186.90
Purchase #5	$235.25	3.624%	$243.7755	$243.78	$243.80	$243.80
Purchase #6	$53.92	13.871%	$61.3992	$61.40	$61.40	$61.40
Purchase #7	$137.42	3.266%	$141.9081	$141.91	$141.90	$141.90
7 purchase totals =	$1,068.12		$1,138.5679	$1,138.58	$1,138.60	$1,138.60