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	$105.35	5.343%	$110.9789	$110.98	$111.00	$111.00
Purchase #2	$141.98	6.379%	$151.0369	$151.04	$151.05	$151.00
Purchase #3	$156.65	11.491%	$174.6507	$174.65	$174.65	$174.70
Purchase #4	$38.25	7.646%	$41.1746	$41.17	$41.15	$41.20
Purchase #5	$232.69	5.115%	$244.5921	$244.59	$244.60	$244.60
Purchase #6	$174.26	8.331%	$188.7776	$188.78	$188.80	$188.80
Purchase #7	$86.84	3.374%	$89.77	$89.77	$89.75	$89.80
7 purchase totals =	$936.02		$1,000.9808	$1,000.98	$1,001.00	$1,001.10