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	$184.72	13.586%	$209.8161	$209.82	$209.80	$209.80
Purchase #2	$102.41	6.530%	$109.0974	$109.10	$109.10	$109.10
Purchase #3	$74.75	7.773%	$80.5603	$80.56	$80.55	$80.60
Purchase #4	$179.31	13.790%	$204.0368	$204.04	$204.05	$204.00
Purchase #5	$197.87	5.741%	$209.2297	$209.23	$209.25	$209.20
Purchase #6	$227.90	4.505%	$238.1669	$238.17	$238.15	$238.20
Purchase #7	$63.46	3.776%	$65.8562	$65.86	$65.85	$65.90
7 purchase totals =	$1,030.42		$1,116.7634	$1,116.78	$1,116.75	$1,116.80