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	$51.32	4.702%	$53.7331	$53.73	$53.75	$53.70
Purchase #2	$181.76	12.777%	$204.9835	$204.98	$205.00	$205.00
Purchase #3	$119.76	7.627%	$128.8941	$128.89	$128.90	$128.90
Purchase #4	$176.47	13.522%	$200.3323	$200.33	$200.35	$200.30
Purchase #5	$233.86	7.574%	$251.5726	$251.57	$251.55	$251.60
Purchase #6	$242.68	3.618%	$251.4602	$251.46	$251.45	$251.50
Purchase #7	$61.99	6.174%	$65.8173	$65.82	$65.80	$65.80
7 purchase totals =	$1,067.84		$1,156.7931	$1,156.78	$1,156.80	$1,156.80