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	$143.76	3.826%	$149.2603	$149.26	$149.25	$149.30
Purchase #2	$77.33	6.139%	$82.0773	$82.08	$82.10	$82.10
Purchase #3	$135.71	7.617%	$146.047	$146.05	$146.05	$146.00
Purchase #4	$54.67	8.236%	$59.1726	$59.17	$59.15	$59.20
Purchase #5	$97.64	3.171%	$100.7362	$100.74	$100.75	$100.70
Purchase #6	$150.94	6.427%	$160.6409	$160.64	$160.65	$160.60
Purchase #7	$67.83	3.258%	$70.0399	$70.04	$70.05	$70.00
7 purchase totals =	$727.88		$767.9742	$767.98	$768.00	$767.90