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	$62.28	11.646%	$69.5331	$69.53	$69.55	$69.50
Purchase #2	$57.48	3.327%	$59.3924	$59.39	$59.40	$59.40
Purchase #3	$225.97	6.342%	$240.301	$240.30	$240.30	$240.30
Purchase #4	$32.58	3.782%	$33.8122	$33.81	$33.80	$33.80
Purchase #5	$237.46	3.116%	$244.8593	$244.86	$244.85	$244.90
Purchase #6	$188.88	12.308%	$212.1274	$212.13	$212.15	$212.10
Purchase #7	$6.86	7.764%	$7.3926	$7.39	$7.40	$7.40
7 purchase totals =	$811.51		$867.4180	$867.41	$867.45	$867.40