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	$203.37	11.109%	$225.9624	$225.96	$225.95	$226.00
Purchase #2	$27.46	5.148%	$28.8736	$28.87	$28.85	$28.90
Purchase #3	$183.51	3.729%	$190.3531	$190.35	$190.35	$190.40
Purchase #4	$55.49	3.178%	$57.2535	$57.25	$57.25	$57.30
Purchase #5	$41.81	12.213%	$46.9163	$46.92	$46.90	$46.90
Purchase #6	$217.78	3.704%	$225.8466	$225.85	$225.85	$225.80
Purchase #7	$97.83	11.563%	$109.1421	$109.14	$109.15	$109.10
7 purchase totals =	$827.25		$884.3476	$884.34	$884.30	$884.40