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	$146.80	5.109%	$154.3	$154.30	$154.30	$154.30
Purchase #2	$146.38	13.289%	$165.8324	$165.83	$165.85	$165.80
Purchase #3	$209.40	4.601%	$219.0345	$219.03	$219.05	$219.00
Purchase #4	$57.94	11.193%	$64.4252	$64.43	$64.45	$64.40
Purchase #5	$163.25	13.137%	$184.6962	$184.70	$184.70	$184.70
Purchase #6	$212.48	4.761%	$222.5962	$222.60	$222.60	$222.60
Purchase #7	$80.80	11.336%	$89.9595	$89.96	$89.95	$90.00
7 purchase totals =	$1,017.05		$1,100.8440	$1,100.85	$1,100.90	$1,100.80