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	$103.60	10.753%	$114.7401	$114.74	$114.75	$114.70
Purchase #2	$47.43	6.367%	$50.4499	$50.45	$50.45	$50.40
Purchase #3	$236.62	3.791%	$245.5903	$245.59	$245.60	$245.60
Purchase #4	$85.76	4.539%	$89.6526	$89.65	$89.65	$89.70
Purchase #5	$143.54	10.564%	$158.7036	$158.70	$158.70	$158.70
Purchase #6	$38.69	12.805%	$43.6443	$43.64	$43.65	$43.60
Purchase #7	$49.58	3.156%	$51.1447	$51.14	$51.15	$51.10
7 purchase totals =	$705.22		$753.9255	$753.91	$753.95	$753.80