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	$96.96	9.242%	$105.921	$105.92	$105.90	$105.90
Purchase #2	$167.43	3.203%	$172.7928	$172.79	$172.80	$172.80
Purchase #3	$68.62	3.570%	$71.0697	$71.07	$71.05	$71.10
Purchase #4	$186.63	6.160%	$198.1264	$198.13	$198.15	$198.10
Purchase #5	$170.88	7.141%	$183.0825	$183.08	$183.10	$183.10
Purchase #6	$128.40	8.168%	$138.8877	$138.89	$138.90	$138.90
Purchase #7	$48.98	11.318%	$54.5236	$54.52	$54.50	$54.50
7 purchase totals =	$867.90		$924.4037	$924.40	$924.40	$924.40