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	$187.92	6.334%	$199.8229	$199.82	$199.80	$199.80
Purchase #2	$165.93	11.745%	$185.4185	$185.42	$185.40	$185.40
Purchase #3	$13.70	3.395%	$14.1651	$14.17	$14.15	$14.20
Purchase #4	$89.84	13.702%	$102.1499	$102.15	$102.15	$102.10
Purchase #5	$227.78	6.383%	$242.3192	$242.32	$242.30	$242.30
Purchase #6	$117.52	4.710%	$123.0552	$123.06	$123.05	$123.10
Purchase #7	$6.65	3.427%	$6.8779	$6.88	$6.90	$6.90
7 purchase totals =	$809.34		$873.8087	$873.82	$873.75	$873.80