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	$46.71	11.586%	$52.1218	$52.12	$52.10	$52.10
Purchase #2	$236.35	12.666%	$266.2861	$266.29	$266.30	$266.30
Purchase #3	$102.74	6.224%	$109.1345	$109.13	$109.15	$109.10
Purchase #4	$150.90	12.495%	$169.755	$169.76	$169.75	$169.80
Purchase #5	$162.73	10.410%	$179.6702	$179.67	$179.65	$179.70
Purchase #6	$131.76	9.103%	$143.7541	$143.75	$143.75	$143.80
Purchase #7	$154.33	12.481%	$173.5919	$173.59	$173.60	$173.60
7 purchase totals =	$985.52		$1,094.3136	$1,094.31	$1,094.30	$1,094.40