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	$42.39	6.793%	$45.2696	$45.27	$45.25	$45.30
Purchase #2	$114.88	13.585%	$130.4864	$130.49	$130.50	$130.50
Purchase #3	$148.63	11.779%	$166.1371	$166.14	$166.15	$166.10
Purchase #4	$72.50	4.804%	$75.9829	$75.98	$76.00	$76.00
Purchase #5	$206.40	4.856%	$216.4228	$216.42	$216.40	$216.40
Purchase #6	$105.45	6.316%	$112.1102	$112.11	$112.10	$112.10
Purchase #7	$138.33	10.844%	$153.3305	$153.33	$153.35	$153.30
7 purchase totals =	$828.58		$899.7395	$899.74	$899.75	$899.70