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	$90.69	13.635%	$103.0556	$103.06	$103.05	$103.10
Purchase #2	$28.31	5.816%	$29.9565	$29.96	$29.95	$30.00
Purchase #3	$23.79	8.469%	$25.8048	$25.80	$25.80	$25.80
Purchase #4	$36.59	3.234%	$37.7733	$37.77	$37.75	$37.80
Purchase #5	$167.38	13.744%	$190.3847	$190.38	$190.40	$190.40
Purchase #6	$40.67	6.197%	$43.1903	$43.19	$43.20	$43.20
Purchase #7	$11.97	8.780%	$13.021	$13.02	$13.00	$13.00
7 purchase totals =	$399.40		$443.1862	$443.18	$443.15	$443.30