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	$173.84	12.112%	$194.8955	$194.90	$194.90	$194.90
Purchase #2	$185.61	12.752%	$209.279	$209.28	$209.30	$209.30
Purchase #3	$39.89	6.346%	$42.4214	$42.42	$42.40	$42.40
Purchase #4	$249.90	10.134%	$275.2249	$275.22	$275.20	$275.20
Purchase #5	$45.59	5.354%	$48.0309	$48.03	$48.05	$48.00
Purchase #6	$25.60	5.699%	$27.0589	$27.06	$27.05	$27.10
Purchase #7	$68.57	13.842%	$78.0615	$78.06	$78.05	$78.10
7 purchase totals =	$789.00		$874.9721	$874.97	$874.95	$875.00