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	$96.92	13.821%	$110.3153	$110.32	$110.30	$110.30
Purchase #2	$103.83	9.490%	$113.6835	$113.68	$113.70	$113.70
Purchase #3	$200.98	13.181%	$227.4712	$227.47	$227.45	$227.50
Purchase #4	$88.28	9.627%	$96.7787	$96.78	$96.80	$96.80
Purchase #5	$218.87	4.396%	$228.4915	$228.49	$228.50	$228.50
Purchase #6	$157.35	6.458%	$167.5117	$167.51	$167.50	$167.50
Purchase #7	$139.31	4.724%	$145.891	$145.89	$145.90	$145.90
7 purchase totals =	$1,005.54		$1,090.1429	$1,090.14	$1,090.15	$1,090.20