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	$191.31	10.147%	$210.7222	$210.72	$210.70	$210.70
Purchase #2	$130.44	3.711%	$135.2806	$135.28	$135.30	$135.30
Purchase #3	$101.67	3.651%	$105.382	$105.38	$105.40	$105.40
Purchase #4	$214.46	3.615%	$222.2127	$222.21	$222.20	$222.20
Purchase #5	$206.98	13.723%	$235.3839	$235.38	$235.40	$235.40
Purchase #6	$65.69	5.598%	$69.3673	$69.37	$69.35	$69.40
Purchase #7	$64.60	10.661%	$71.487	$71.49	$71.50	$71.50
7 purchase totals =	$975.15		$1,049.8357	$1,049.83	$1,049.85	$1,049.90