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	$173.67	10.567%	$192.0217	$192.02	$192.00	$192.00
Purchase #2	$104.63	8.781%	$113.8176	$113.82	$113.80	$113.80
Purchase #3	$179.52	13.235%	$203.2795	$203.28	$203.30	$203.30
Purchase #4	$152.52	8.642%	$165.7008	$165.70	$165.70	$165.70
Purchase #5	$80.63	10.581%	$89.1615	$89.16	$89.15	$89.20
Purchase #6	$84.73	6.669%	$90.3806	$90.38	$90.40	$90.40
Purchase #7	$227.58	6.375%	$242.0882	$242.09	$242.10	$242.10
7 purchase totals =	$1,003.28		$1,096.4499	$1,096.45	$1,096.45	$1,096.50