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	$220.75	10.139%	$243.1318	$243.13	$243.15	$243.10
Purchase #2	$5.55	10.739%	$6.146	$6.15	$6.15	$6.10
Purchase #3	$90.94	5.103%	$95.5807	$95.58	$95.60	$95.60
Purchase #4	$177.69	3.571%	$184.0353	$184.04	$184.05	$184.00
Purchase #5	$136.36	10.778%	$151.0569	$151.06	$151.05	$151.10
Purchase #6	$27.73	13.550%	$31.4874	$31.49	$31.50	$31.50
Purchase #7	$39.98	5.108%	$42.0222	$42.02	$42.00	$42.00
7 purchase totals =	$699.00		$753.4603	$753.47	$753.50	$753.40