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	$98.38	8.366%	$106.6105	$106.61	$106.60	$106.60
Purchase #2	$139.47	6.203%	$148.1213	$148.12	$148.10	$148.10
Purchase #3	$123.31	3.394%	$127.4951	$127.50	$127.50	$127.50
Purchase #4	$202.55	4.250%	$211.1584	$211.16	$211.15	$211.20
Purchase #5	$74.96	7.871%	$80.8601	$80.86	$80.85	$80.90
Purchase #6	$105.40	13.112%	$119.22	$119.22	$119.20	$119.20
Purchase #7	$188.55	12.623%	$212.3507	$212.35	$212.35	$212.40
7 purchase totals =	$932.62		$1,005.8161	$1,005.82	$1,005.75	$1,005.90