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	$188.66	6.423%	$200.7776	$200.78	$200.80	$200.80
Purchase #2	$6.66	6.123%	$7.0678	$7.07	$7.05	$7.10
Purchase #3	$228.42	10.219%	$251.7622	$251.76	$251.75	$251.80
Purchase #4	$105.99	3.415%	$109.6096	$109.61	$109.60	$109.60
Purchase #5	$105.91	5.640%	$111.8833	$111.88	$111.90	$111.90
Purchase #6	$204.67	5.114%	$215.1368	$215.14	$215.15	$215.10
Purchase #7	$169.61	3.560%	$175.6481	$175.65	$175.65	$175.60
7 purchase totals =	$1,009.92		$1,071.8854	$1,071.89	$1,071.90	$1,071.90