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	$83.48	7.288%	$89.564	$89.56	$89.55	$89.60
Purchase #2	$130.46	13.284%	$147.7903	$147.79	$147.80	$147.80
Purchase #3	$178.56	13.583%	$202.8138	$202.81	$202.80	$202.80
Purchase #4	$111.44	8.783%	$121.2278	$121.23	$121.25	$121.20
Purchase #5	$135.35	11.236%	$150.5579	$150.56	$150.55	$150.60
Purchase #6	$195.65	13.731%	$222.5147	$222.51	$222.50	$222.50
Purchase #7	$96.47	6.131%	$102.3846	$102.38	$102.40	$102.40
7 purchase totals =	$931.41		$1,036.8531	$1,036.84	$1,036.85	$1,036.90