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	$94.72	5.751%	$100.1673	$100.17	$100.15	$100.20
Purchase #2	$26.65	6.590%	$28.4062	$28.41	$28.40	$28.40
Purchase #3	$145.35	6.498%	$154.7948	$154.79	$154.80	$154.80
Purchase #4	$50.62	8.401%	$54.8726	$54.87	$54.85	$54.90
Purchase #5	$206.44	13.859%	$235.0505	$235.05	$235.05	$235.10
Purchase #6	$43.72	3.629%	$45.3066	$45.31	$45.30	$45.30
Purchase #7	$126.49	3.456%	$130.8615	$130.86	$130.85	$130.90
7 purchase totals =	$693.99		$749.4595	$749.46	$749.40	$749.60