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	$130.32	9.537%	$142.7486	$142.75	$142.75	$142.70
Purchase #2	$101.35	7.835%	$109.2908	$109.29	$109.30	$109.30
Purchase #3	$50.82	9.217%	$55.5041	$55.50	$55.50	$55.50
Purchase #4	$178.27	4.127%	$185.6272	$185.63	$185.65	$185.60
Purchase #5	$234.84	3.411%	$242.8504	$242.85	$242.85	$242.90
Purchase #6	$38.25	11.291%	$42.5688	$42.57	$42.55	$42.60
Purchase #7	$101.34	9.354%	$110.8193	$110.82	$110.80	$110.80
7 purchase totals =	$835.19		$889.4092	$889.41	$889.40	$889.40