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	$238.71	6.169%	$253.436	$253.44	$253.45	$253.40
Purchase #2	$78.41	5.236%	$82.5155	$82.52	$82.50	$82.50
Purchase #3	$18.50	6.285%	$19.6627	$19.66	$19.65	$19.70
Purchase #4	$199.29	12.485%	$224.1714	$224.17	$224.15	$224.20
Purchase #5	$92.52	10.590%	$102.3179	$102.32	$102.30	$102.30
Purchase #6	$81.50	9.735%	$89.434	$89.43	$89.45	$89.40
Purchase #7	$230.44	10.490%	$254.6132	$254.61	$254.60	$254.60
7 purchase totals =	$939.37		$1,026.1507	$1,026.15	$1,026.10	$1,026.10