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	$186.37	5.654%	$196.9074	$196.91	$196.90	$196.90
Purchase #2	$34.90	6.179%	$37.0565	$37.06	$37.05	$37.10
Purchase #3	$247.90	6.433%	$263.8474	$263.85	$263.85	$263.80
Purchase #4	$241.35	10.311%	$266.2356	$266.24	$266.25	$266.20
Purchase #5	$91.36	6.277%	$97.0947	$97.09	$97.10	$97.10
Purchase #6	$145.36	5.277%	$153.0306	$153.03	$153.05	$153.00
Purchase #7	$71.28	8.642%	$77.44	$77.44	$77.45	$77.40
7 purchase totals =	$1,018.52		$1,091.6122	$1,091.62	$1,091.65	$1,091.50