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	$130.92	5.764%	$138.4662	$138.47	$138.45	$138.50
Purchase #2	$64.60	11.390%	$71.9579	$71.96	$71.95	$72.00
Purchase #3	$84.68	10.515%	$93.5841	$93.58	$93.60	$93.60
Purchase #4	$53.60	11.813%	$59.9318	$59.93	$59.95	$59.90
Purchase #5	$71.84	6.844%	$76.7567	$76.76	$76.75	$76.80
Purchase #6	$80.38	6.149%	$85.3226	$85.32	$85.30	$85.30
Purchase #7	$139.72	11.841%	$156.2642	$156.26	$156.25	$156.30
7 purchase totals =	$625.74		$682.2835	$682.28	$682.25	$682.40