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	$159.57	10.264%	$175.9483	$175.95	$175.95	$175.90
Purchase #2	$78.41	5.245%	$82.5226	$82.52	$82.50	$82.50
Purchase #3	$221.77	12.485%	$249.458	$249.46	$249.45	$249.50
Purchase #4	$79.33	12.874%	$89.5429	$89.54	$89.55	$89.50
Purchase #5	$186.30	13.815%	$212.0373	$212.04	$212.05	$212.00
Purchase #6	$103.52	5.804%	$109.5283	$109.53	$109.55	$109.50
Purchase #7	$212.66	13.609%	$241.6009	$241.60	$241.60	$241.60
7 purchase totals =	$1,041.56		$1,160.6383	$1,160.64	$1,160.65	$1,160.50