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	$214.88	10.374%	$237.1717	$237.17	$237.15	$237.20
Purchase #2	$250.34	12.178%	$280.8264	$280.83	$280.85	$280.80
Purchase #3	$114.52	11.383%	$127.5558	$127.56	$127.55	$127.60
Purchase #4	$48.73	3.161%	$50.2704	$50.27	$50.25	$50.30
Purchase #5	$23.55	12.593%	$26.5157	$26.52	$26.50	$26.50
Purchase #6	$107.25	9.313%	$117.2382	$117.24	$117.25	$117.20
Purchase #7	$97.93	8.109%	$105.8711	$105.87	$105.85	$105.90
7 purchase totals =	$857.20		$945.4493	$945.46	$945.40	$945.50