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	$76.34	4.383%	$79.686	$79.69	$79.70	$79.70
Purchase #2	$110.93	9.590%	$121.5682	$121.57	$121.55	$121.60
Purchase #3	$37.74	6.267%	$40.1052	$40.11	$40.10	$40.10
Purchase #4	$92.52	9.191%	$101.0235	$101.02	$101.00	$101.00
Purchase #5	$178.42	4.182%	$185.8815	$185.88	$185.90	$185.90
Purchase #6	$55.63	10.334%	$61.3788	$61.38	$61.40	$61.40
Purchase #7	$155.42	7.788%	$167.5241	$167.52	$167.50	$167.50
7 purchase totals =	$707.00		$757.1673	$757.17	$757.15	$757.20