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	$139.53	10.337%	$153.9532	$153.95	$153.95	$154.00
Purchase #2	$167.58	10.792%	$185.6652	$185.67	$185.65	$185.70
Purchase #3	$80.53	10.686%	$89.1354	$89.14	$89.15	$89.10
Purchase #4	$226.39	12.221%	$254.0571	$254.06	$254.05	$254.10
Purchase #5	$242.25	11.359%	$269.7672	$269.77	$269.75	$269.80
Purchase #6	$225.65	10.760%	$249.9299	$249.93	$249.95	$249.90
Purchase #7	$68.36	13.864%	$77.8374	$77.84	$77.85	$77.80
7 purchase totals =	$1,150.29		$1,280.3454	$1,280.36	$1,280.35	$1,280.40