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	$161.60	12.274%	$181.4348	$181.43	$181.45	$181.40
Purchase #2	$169.56	10.467%	$187.3078	$187.31	$187.30	$187.30
Purchase #3	$115.99	7.718%	$124.9421	$124.94	$124.95	$124.90
Purchase #4	$223.45	9.392%	$244.4364	$244.44	$244.45	$244.40
Purchase #5	$12.70	4.635%	$13.2886	$13.29	$13.30	$13.30
Purchase #6	$15.90	4.144%	$16.5589	$16.56	$16.55	$16.60
Purchase #7	$145.34	10.323%	$160.3434	$160.34	$160.35	$160.30
7 purchase totals =	$844.54		$928.3120	$928.31	$928.35	$928.20