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	$97.84	11.787%	$109.3724	$109.37	$109.35	$109.40
Purchase #2	$70.31	11.481%	$78.3823	$78.38	$78.40	$78.40
Purchase #3	$184.91	10.676%	$204.651	$204.65	$204.65	$204.70
Purchase #4	$223.66	10.181%	$246.4308	$246.43	$246.45	$246.40
Purchase #5	$215.28	4.310%	$224.5586	$224.56	$224.55	$224.60
Purchase #6	$142.75	4.300%	$148.8883	$148.89	$148.90	$148.90
Purchase #7	$149.25	12.456%	$167.8406	$167.84	$167.85	$167.80
7 purchase totals =	$1,084.00		$1,180.1240	$1,180.12	$1,180.15	$1,180.20