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	$149.45	13.490%	$169.6108	$169.61	$169.60	$169.60
Purchase #2	$229.37	5.486%	$241.9532	$241.95	$241.95	$242.00
Purchase #3	$103.77	5.328%	$109.2989	$109.30	$109.30	$109.30
Purchase #4	$99.65	11.617%	$111.2263	$111.23	$111.25	$111.20
Purchase #5	$171.71	5.718%	$181.5284	$181.53	$181.55	$181.50
Purchase #6	$234.76	13.769%	$267.0841	$267.08	$267.10	$267.10
Purchase #7	$58.36	5.848%	$61.7729	$61.77	$61.75	$61.80
7 purchase totals =	$1,047.07		$1,142.4746	$1,142.47	$1,142.50	$1,142.50