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	$95.29	8.593%	$103.4783	$103.48	$103.50	$103.50
Purchase #2	$151.73	8.162%	$164.1142	$164.11	$164.10	$164.10
Purchase #3	$203.35	7.736%	$219.0812	$219.08	$219.10	$219.10
Purchase #4	$74.36	12.214%	$83.4423	$83.44	$83.45	$83.40
Purchase #5	$174.50	4.236%	$181.8918	$181.89	$181.90	$181.90
Purchase #6	$185.77	3.789%	$192.8088	$192.81	$192.80	$192.80
Purchase #7	$228.33	11.516%	$254.6245	$254.62	$254.60	$254.60
7 purchase totals =	$1,113.33		$1,199.4411	$1,199.43	$1,199.45	$1,199.40