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	$167.41	13.399%	$189.8413	$189.84	$189.85	$189.80
Purchase #2	$165.54	11.398%	$184.4082	$184.41	$184.40	$184.40
Purchase #3	$18.97	3.653%	$19.663	$19.66	$19.65	$19.70
Purchase #4	$182.93	3.189%	$188.7636	$188.76	$188.75	$188.80
Purchase #5	$82.98	11.586%	$92.5941	$92.59	$92.60	$92.60
Purchase #6	$72.93	7.315%	$78.2648	$78.26	$78.25	$78.30
Purchase #7	$84.57	12.852%	$95.4389	$95.44	$95.45	$95.40
7 purchase totals =	$775.33		$848.9739	$848.96	$848.95	$849.00