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	$168.31	8.209%	$182.1266	$182.13	$182.15	$182.10
Purchase #2	$137.62	13.369%	$156.0184	$156.02	$156.00	$156.00
Purchase #3	$197.29	10.689%	$218.3783	$218.38	$218.40	$218.40
Purchase #4	$239.78	6.674%	$255.7829	$255.78	$255.80	$255.80
Purchase #5	$116.47	6.417%	$123.9439	$123.94	$123.95	$123.90
Purchase #6	$41.98	11.369%	$46.7527	$46.75	$46.75	$46.80
Purchase #7	$222.28	6.742%	$237.2661	$237.27	$237.25	$237.30
7 purchase totals =	$1,123.73		$1,220.2689	$1,220.27	$1,220.30	$1,220.30