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	$243.70	8.663%	$264.8117	$264.81	$264.80	$264.80
Purchase #2	$18.78	8.247%	$20.3288	$20.33	$20.35	$20.30
Purchase #3	$176.55	6.711%	$188.3983	$188.40	$188.40	$188.40
Purchase #4	$54.81	11.630%	$61.1844	$61.18	$61.20	$61.20
Purchase #5	$117.37	8.816%	$127.7173	$127.72	$127.70	$127.70
Purchase #6	$237.26	3.461%	$245.4716	$245.47	$245.45	$245.50
Purchase #7	$172.66	3.524%	$178.7445	$178.74	$178.75	$178.70
7 purchase totals =	$1,021.13		$1,086.6566	$1,086.65	$1,086.65	$1,086.60