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	$150.59	7.737%	$162.2411	$162.24	$162.25	$162.20
Purchase #2	$111.38	11.706%	$124.4181	$124.42	$124.40	$124.40
Purchase #3	$162.86	7.206%	$174.5957	$174.60	$174.60	$174.60
Purchase #4	$89.95	6.595%	$95.8822	$95.88	$95.90	$95.90
Purchase #5	$147.56	13.386%	$167.3124	$167.31	$167.30	$167.30
Purchase #6	$70.90	5.555%	$74.8385	$74.84	$74.85	$74.80
Purchase #7	$166.35	11.484%	$185.4536	$185.45	$185.45	$185.50
7 purchase totals =	$899.59		$984.7416	$984.74	$984.75	$984.70