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	$89.27	13.821%	$101.608	$101.61	$101.60	$101.60
Purchase #2	$148.38	7.478%	$159.4759	$159.48	$159.50	$159.50
Purchase #3	$250.75	4.179%	$261.2288	$261.23	$261.25	$261.20
Purchase #4	$187.44	13.537%	$212.8138	$212.81	$212.80	$212.80
Purchase #5	$186.35	7.643%	$200.5927	$200.59	$200.60	$200.60
Purchase #6	$46.71	5.491%	$49.2748	$49.27	$49.25	$49.30
Purchase #7	$27.58	4.552%	$28.8354	$28.84	$28.85	$28.80
7 purchase totals =	$936.48		$1,013.8294	$1,013.83	$1,013.85	$1,013.80