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	$152.34	9.807%	$167.28	$167.28	$167.30	$167.30
Purchase #2	$108.59	5.697%	$114.7764	$114.78	$114.80	$114.80
Purchase #3	$132.96	12.778%	$149.9496	$149.95	$149.95	$149.90
Purchase #4	$89.44	10.384%	$98.7274	$98.73	$98.75	$98.70
Purchase #5	$91.36	13.131%	$103.3565	$103.36	$103.35	$103.40
Purchase #6	$104.34	11.692%	$116.5394	$116.54	$116.55	$116.50
Purchase #7	$172.30	7.528%	$185.2707	$185.27	$185.25	$185.30
7 purchase totals =	$851.33		$935.9000	$935.91	$935.95	$935.90