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	$94.51	7.707%	$101.7939	$101.79	$101.80	$101.80
Purchase #2	$82.66	9.365%	$90.4011	$90.40	$90.40	$90.40
Purchase #3	$106.51	4.395%	$111.1911	$111.19	$111.20	$111.20
Purchase #4	$19.28	4.355%	$20.1196	$20.12	$20.10	$20.10
Purchase #5	$71.47	13.397%	$81.0448	$81.04	$81.05	$81.00
Purchase #6	$123.42	12.833%	$139.2585	$139.26	$139.25	$139.30
Purchase #7	$246.77	7.197%	$264.53	$264.53	$264.55	$264.50
7 purchase totals =	$744.62		$808.3390	$808.33	$808.35	$808.30