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	$156.42	7.716%	$168.4894	$168.49	$168.50	$168.50
Purchase #2	$61.75	6.272%	$65.623	$65.62	$65.60	$65.60
Purchase #3	$227.45	4.466%	$237.6079	$237.61	$237.60	$237.60
Purchase #4	$93.63	10.611%	$103.5651	$103.57	$103.55	$103.60
Purchase #5	$94.57	8.673%	$102.7721	$102.77	$102.75	$102.80
Purchase #6	$161.64	8.447%	$175.2937	$175.29	$175.30	$175.30
Purchase #7	$200.54	11.477%	$223.556	$223.56	$223.55	$223.60
7 purchase totals =	$996.00		$1,076.9072	$1,076.91	$1,076.85	$1,077.00