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	$53.74	9.823%	$59.0189	$59.02	$59.00	$59.00
Purchase #2	$50.33	11.818%	$56.278	$56.28	$56.30	$56.30
Purchase #3	$220.50	7.570%	$237.1919	$237.19	$237.20	$237.20
Purchase #4	$228.73	5.594%	$241.5252	$241.53	$241.55	$241.50
Purchase #5	$74.92	6.836%	$80.0415	$80.04	$80.05	$80.00
Purchase #6	$234.86	4.429%	$245.2619	$245.26	$245.25	$245.30
Purchase #7	$86.78	3.103%	$89.4728	$89.47	$89.45	$89.50
7 purchase totals =	$949.86		$1,008.7902	$1,008.79	$1,008.80	$1,008.80