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	$184.87	13.626%	$210.0604	$210.06	$210.05	$210.10
Purchase #2	$100.82	13.721%	$114.6535	$114.65	$114.65	$114.70
Purchase #3	$51.69	11.181%	$57.4695	$57.47	$57.45	$57.50
Purchase #4	$123.56	12.304%	$138.7628	$138.76	$138.75	$138.80
Purchase #5	$152.61	9.620%	$167.2911	$167.29	$167.30	$167.30
Purchase #6	$62.73	8.460%	$68.037	$68.04	$68.05	$68.00
Purchase #7	$157.25	9.590%	$172.3303	$172.33	$172.35	$172.30
7 purchase totals =	$833.53		$928.6046	$928.60	$928.60	$928.70