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	$228.31	7.813%	$246.1479	$246.15	$246.15	$246.10
Purchase #2	$117.81	3.620%	$122.0747	$122.07	$122.05	$122.10
Purchase #3	$103.79	7.814%	$111.9002	$111.90	$111.90	$111.90
Purchase #4	$78.66	8.128%	$85.0535	$85.05	$85.05	$85.10
Purchase #5	$150.47	7.204%	$161.3099	$161.31	$161.30	$161.30
Purchase #6	$155.31	3.292%	$160.4228	$160.42	$160.40	$160.40
Purchase #7	$174.85	8.412%	$189.5584	$189.56	$189.55	$189.60
7 purchase totals =	$1,009.20		$1,076.4674	$1,076.46	$1,076.40	$1,076.50