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	$96.35	5.644%	$101.788	$101.79	$101.80	$101.80
Purchase #2	$67.52	7.111%	$72.3213	$72.32	$72.30	$72.30
Purchase #3	$211.50	11.280%	$235.3572	$235.36	$235.35	$235.40
Purchase #4	$65.28	7.407%	$70.1153	$70.12	$70.10	$70.10
Purchase #5	$18.81	11.808%	$21.0311	$21.03	$21.05	$21.00
Purchase #6	$222.55	9.824%	$244.4133	$244.41	$244.40	$244.40
Purchase #7	$112.66	9.868%	$123.7773	$123.78	$123.80	$123.80
7 purchase totals =	$794.67		$868.8035	$868.81	$868.80	$868.80