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	$53.42	5.596%	$56.4094	$56.41	$56.40	$56.40
Purchase #2	$91.83	11.330%	$102.2343	$102.23	$102.25	$102.20
Purchase #3	$248.72	11.123%	$276.3851	$276.39	$276.40	$276.40
Purchase #4	$241.30	9.215%	$263.5358	$263.54	$263.55	$263.50
Purchase #5	$101.31	8.242%	$109.66	$109.66	$109.65	$109.70
Purchase #6	$131.32	4.723%	$137.5222	$137.52	$137.50	$137.50
Purchase #7	$134.84	11.814%	$150.77	$150.77	$150.75	$150.80
7 purchase totals =	$1,002.74		$1,096.5168	$1,096.52	$1,096.50	$1,096.50