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	$246.88	3.196%	$254.7703	$254.77	$254.75	$254.80
Purchase #2	$30.76	6.230%	$32.6763	$32.68	$32.70	$32.70
Purchase #3	$144.77	6.765%	$154.5637	$154.56	$154.55	$154.60
Purchase #4	$72.44	13.786%	$82.4266	$82.43	$82.45	$82.40
Purchase #5	$178.74	10.616%	$197.715	$197.72	$197.70	$197.70
Purchase #6	$156.82	6.424%	$166.8941	$166.89	$166.90	$166.90
Purchase #7	$244.82	13.385%	$277.5892	$277.59	$277.60	$277.60
7 purchase totals =	$1,075.23		$1,166.6352	$1,166.64	$1,166.65	$1,166.70