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	$52.69	13.131%	$59.6087	$59.61	$59.60	$59.60
Purchase #2	$41.60	8.180%	$45.0029	$45.00	$45.00	$45.00
Purchase #3	$101.39	4.657%	$106.1117	$106.11	$106.10	$106.10
Purchase #4	$18.41	8.528%	$19.98	$19.98	$20.00	$20.00
Purchase #5	$98.97	12.698%	$111.5372	$111.54	$111.55	$111.50
Purchase #6	$25.28	10.532%	$27.9425	$27.94	$27.95	$27.90
Purchase #7	$220.64	3.383%	$228.1043	$228.10	$228.10	$228.10
7 purchase totals =	$558.98		$598.2873	$598.28	$598.30	$598.20