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	$189.56	5.554%	$200.0882	$200.09	$200.10	$200.10
Purchase #2	$72.33	8.557%	$78.5193	$78.52	$78.50	$78.50
Purchase #3	$244.69	6.813%	$261.3607	$261.36	$261.35	$261.40
Purchase #4	$163.61	10.729%	$181.1637	$181.16	$181.15	$181.20
Purchase #5	$15.51	3.173%	$16.0021	$16.00	$16.00	$16.00
Purchase #6	$83.28	3.698%	$86.3597	$86.36	$86.35	$86.40
Purchase #7	$173.98	12.569%	$195.8475	$195.85	$195.85	$195.80
7 purchase totals =	$942.96		$1,019.3412	$1,019.34	$1,019.30	$1,019.40