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	$143.88	5.712%	$152.0984	$152.10	$152.10	$152.10
Purchase #2	$145.45	6.693%	$155.185	$155.19	$155.20	$155.20
Purchase #3	$56.84	5.236%	$59.8161	$59.82	$59.80	$59.80
Purchase #4	$137.76	9.839%	$151.3142	$151.31	$151.30	$151.30
Purchase #5	$246.39	3.130%	$254.102	$254.10	$254.10	$254.10
Purchase #6	$209.37	10.269%	$230.8702	$230.87	$230.85	$230.90
Purchase #7	$93.75	9.322%	$102.4894	$102.49	$102.50	$102.50
7 purchase totals =	$1,033.44		$1,105.8753	$1,105.88	$1,105.85	$1,105.90