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	$118.98	10.374%	$131.323	$131.32	$131.30	$131.30
Purchase #2	$223.59	3.510%	$231.438	$231.44	$231.45	$231.40
Purchase #3	$173.54	10.490%	$191.7443	$191.74	$191.75	$191.70
Purchase #4	$102.44	7.841%	$110.4723	$110.47	$110.45	$110.50
Purchase #5	$98.98	7.603%	$106.5054	$106.51	$106.50	$106.50
Purchase #6	$181.27	10.554%	$200.4012	$200.40	$200.40	$200.40
Purchase #7	$78.75	6.529%	$83.8916	$83.89	$83.90	$83.90
7 purchase totals =	$977.55		$1,055.7758	$1,055.77	$1,055.75	$1,055.70