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	$89.63	13.494%	$101.7247	$101.72	$101.70	$101.70
Purchase #2	$96.31	8.799%	$104.7843	$104.78	$104.80	$104.80
Purchase #3	$153.25	12.134%	$171.8454	$171.85	$171.85	$171.80
Purchase #4	$80.92	8.467%	$87.7715	$87.77	$87.75	$87.80
Purchase #5	$213.55	13.724%	$242.8576	$242.86	$242.85	$242.90
Purchase #6	$82.73	4.190%	$86.1964	$86.20	$86.20	$86.20
Purchase #7	$204.54	6.803%	$218.4549	$218.45	$218.45	$218.50
7 purchase totals =	$920.93		$1,013.6348	$1,013.63	$1,013.60	$1,013.70