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	$181.31	10.782%	$200.8588	$200.86	$200.85	$200.90
Purchase #2	$239.41	4.784%	$250.8634	$250.86	$250.85	$250.90
Purchase #3	$83.58	4.388%	$87.2475	$87.25	$87.25	$87.20
Purchase #4	$85.48	5.118%	$89.8549	$89.85	$89.85	$89.90
Purchase #5	$245.65	7.393%	$263.8109	$263.81	$263.80	$263.80
Purchase #6	$237.80	5.252%	$250.2893	$250.29	$250.30	$250.30
Purchase #7	$10.46	13.727%	$11.8958	$11.90	$11.90	$11.90
7 purchase totals =	$1,083.69		$1,154.8206	$1,154.82	$1,154.80	$1,154.90