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	$180.78	8.249%	$195.6925	$195.69	$195.70	$195.70
Purchase #2	$99.43	11.713%	$111.0762	$111.08	$111.10	$111.10
Purchase #3	$42.40	6.153%	$45.0089	$45.01	$45.00	$45.00
Purchase #4	$96.83	3.559%	$100.2762	$100.28	$100.30	$100.30
Purchase #5	$216.41	7.871%	$233.4436	$233.44	$233.45	$233.40
Purchase #6	$99.46	7.322%	$106.7425	$106.74	$106.75	$106.70
Purchase #7	$13.53	6.333%	$14.3869	$14.39	$14.40	$14.40
7 purchase totals =	$748.84		$806.6268	$806.63	$806.70	$806.60