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	$31.89	4.579%	$33.3502	$33.35	$33.35	$33.40
Purchase #2	$32.79	12.132%	$36.7681	$36.77	$36.75	$36.80
Purchase #3	$21.33	4.542%	$22.2988	$22.30	$22.30	$22.30
Purchase #4	$76.84	8.735%	$83.552	$83.55	$83.55	$83.60
Purchase #5	$70.31	13.866%	$80.0592	$80.06	$80.05	$80.10
Purchase #6	$53.52	11.631%	$59.7449	$59.74	$59.75	$59.70
Purchase #7	$38.71	11.357%	$43.1063	$43.11	$43.10	$43.10
7 purchase totals =	$325.39		$358.8795	$358.88	$358.85	$359.00