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	$93.78	6.120%	$99.5193	$99.52	$99.50	$99.50
Purchase #2	$96.28	7.482%	$103.4837	$103.48	$103.50	$103.50
Purchase #3	$72.56	4.440%	$75.7817	$75.78	$75.80	$75.80
Purchase #4	$62.99	13.227%	$71.3217	$71.32	$71.30	$71.30
Purchase #5	$125.46	5.260%	$132.0592	$132.06	$132.05	$132.10
Purchase #6	$167.45	8.606%	$181.8607	$181.86	$181.85	$181.90
Purchase #7	$64.64	8.724%	$70.2792	$70.28	$70.30	$70.30
7 purchase totals =	$683.16		$734.3055	$734.30	$734.30	$734.40