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	$128.63	13.368%	$145.8253	$145.83	$145.85	$145.80
Purchase #2	$172.82	7.546%	$185.861	$185.86	$185.85	$185.90
Purchase #3	$6.92	6.805%	$7.3909	$7.39	$7.40	$7.40
Purchase #4	$66.53	3.286%	$68.7162	$68.72	$68.70	$68.70
Purchase #5	$98.49	10.465%	$108.797	$108.80	$108.80	$108.80
Purchase #6	$57.44	3.682%	$59.5549	$59.55	$59.55	$59.60
Purchase #7	$198.46	5.152%	$208.6847	$208.68	$208.70	$208.70
7 purchase totals =	$729.29		$784.8300	$784.83	$784.85	$784.90