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	$156.70	11.378%	$174.5293	$174.53	$174.55	$174.50
Purchase #2	$124.37	12.380%	$139.767	$139.77	$139.75	$139.80
Purchase #3	$54.32	13.301%	$61.5451	$61.55	$61.55	$61.50
Purchase #4	$111.67	3.149%	$115.1865	$115.19	$115.20	$115.20
Purchase #5	$59.71	3.173%	$61.6046	$61.60	$61.60	$61.60
Purchase #6	$159.32	7.571%	$171.3821	$171.38	$171.40	$171.40
Purchase #7	$29.39	10.568%	$32.4959	$32.50	$32.50	$32.50
7 purchase totals =	$695.48		$756.5105	$756.52	$756.55	$756.50