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	$86.85	10.290%	$95.7869	$95.79	$95.80	$95.80
Purchase #2	$220.91	11.543%	$246.4096	$246.41	$246.40	$246.40
Purchase #3	$19.26	10.673%	$21.3156	$21.32	$21.30	$21.30
Purchase #4	$45.64	10.332%	$50.3555	$50.36	$50.35	$50.40
Purchase #5	$50.28	10.220%	$55.4186	$55.42	$55.40	$55.40
Purchase #6	$15.41	13.159%	$17.4378	$17.44	$17.45	$17.40
Purchase #7	$172.66	4.580%	$180.5678	$180.57	$180.55	$180.60
7 purchase totals =	$611.01		$667.2918	$667.31	$667.25	$667.30