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	$245.42	8.678%	$266.7175	$266.72	$266.70	$266.70
Purchase #2	$230.27	5.428%	$242.7691	$242.77	$242.75	$242.80
Purchase #3	$79.55	3.761%	$82.5419	$82.54	$82.55	$82.50
Purchase #4	$180.70	9.654%	$198.1448	$198.14	$198.15	$198.10
Purchase #5	$100.82	8.502%	$109.3917	$109.39	$109.40	$109.40
Purchase #6	$164.69	4.752%	$172.5161	$172.52	$172.50	$172.50
Purchase #7	$85.72	4.333%	$89.4342	$89.43	$89.45	$89.40
7 purchase totals =	$1,087.17		$1,161.5153	$1,161.51	$1,161.50	$1,161.40