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	$245.44	11.578%	$273.857	$273.86	$273.85	$273.90
Purchase #2	$67.75	13.490%	$76.8895	$76.89	$76.90	$76.90
Purchase #3	$165.46	5.718%	$174.921	$174.92	$174.90	$174.90
Purchase #4	$173.78	5.245%	$182.8948	$182.89	$182.90	$182.90
Purchase #5	$81.54	12.338%	$91.6004	$91.60	$91.60	$91.60
Purchase #6	$151.79	13.750%	$172.6611	$172.66	$172.65	$172.70
Purchase #7	$220.57	3.439%	$228.1554	$228.16	$228.15	$228.20
7 purchase totals =	$1,106.33		$1,200.9792	$1,200.98	$1,200.95	$1,201.10