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	$90.93	11.252%	$101.1614	$101.16	$101.15	$101.20
Purchase #2	$73.91	8.505%	$80.196	$80.20	$80.20	$80.20
Purchase #3	$181.87	10.267%	$200.5426	$200.54	$200.55	$200.50
Purchase #4	$38.44	12.594%	$43.2811	$43.28	$43.30	$43.30
Purchase #5	$73.89	12.378%	$83.0361	$83.04	$83.05	$83.00
Purchase #6	$50.48	4.115%	$52.5573	$52.56	$52.55	$52.60
Purchase #7	$144.47	12.514%	$162.549	$162.55	$162.55	$162.50
7 purchase totals =	$653.99		$723.3235	$723.33	$723.35	$723.30