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	$82.86	5.541%	$87.4513	$87.45	$87.45	$87.50
Purchase #2	$167.78	12.387%	$188.5629	$188.56	$188.55	$188.60
Purchase #3	$225.50	6.453%	$240.0515	$240.05	$240.05	$240.10
Purchase #4	$199.51	6.453%	$212.3844	$212.38	$212.40	$212.40
Purchase #5	$131.94	13.287%	$149.4709	$149.47	$149.45	$149.50
Purchase #6	$81.64	9.206%	$89.1558	$89.16	$89.15	$89.20
Purchase #7	$247.27	6.654%	$263.7233	$263.72	$263.70	$263.70
7 purchase totals =	$1,136.50		$1,230.8001	$1,230.79	$1,230.75	$1,231.00