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	$42.57	6.367%	$45.2804	$45.28	$45.30	$45.30
Purchase #2	$117.83	4.811%	$123.4988	$123.50	$123.50	$123.50
Purchase #3	$68.32	4.772%	$71.5802	$71.58	$71.60	$71.60
Purchase #4	$73.33	11.699%	$81.9089	$81.91	$81.90	$81.90
Purchase #5	$165.54	5.632%	$174.8632	$174.86	$174.85	$174.90
Purchase #6	$199.76	12.719%	$225.1675	$225.17	$225.15	$225.20
Purchase #7	$162.98	13.602%	$185.1485	$185.15	$185.15	$185.10
7 purchase totals =	$830.33		$907.4475	$907.45	$907.45	$907.50