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	$145.79	4.315%	$152.0808	$152.08	$152.10	$152.10
Purchase #2	$51.56	5.506%	$54.3989	$54.40	$54.40	$54.40
Purchase #3	$120.45	8.133%	$130.2462	$130.25	$130.25	$130.20
Purchase #4	$110.53	8.726%	$120.1748	$120.17	$120.15	$120.20
Purchase #5	$43.80	3.862%	$45.4916	$45.49	$45.50	$45.50
Purchase #6	$174.75	12.679%	$196.9066	$196.91	$196.90	$196.90
Purchase #7	$206.39	9.442%	$225.8773	$225.88	$225.90	$225.90
7 purchase totals =	$853.27		$925.1762	$925.18	$925.20	$925.20