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	$169.25	10.585%	$187.1651	$187.17	$187.15	$187.20
Purchase #2	$250.54	12.120%	$280.9054	$280.91	$280.90	$280.90
Purchase #3	$54.81	13.133%	$62.0082	$62.01	$62.00	$62.00
Purchase #4	$162.60	3.689%	$168.5983	$168.60	$168.60	$168.60
Purchase #5	$142.32	11.635%	$158.8789	$158.88	$158.90	$158.90
Purchase #6	$206.87	6.851%	$221.0427	$221.04	$221.05	$221.00
Purchase #7	$170.47	12.540%	$191.8469	$191.85	$191.85	$191.80
7 purchase totals =	$1,156.86		$1,270.4455	$1,270.46	$1,270.45	$1,270.40