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	$149.76	12.357%	$168.2658	$168.27	$168.25	$168.30
Purchase #2	$42.65	7.423%	$45.8159	$45.82	$45.80	$45.80
Purchase #3	$215.64	3.353%	$222.8704	$222.87	$222.85	$222.90
Purchase #4	$82.59	7.592%	$88.8602	$88.86	$88.85	$88.90
Purchase #5	$137.34	6.236%	$145.9045	$145.90	$145.90	$145.90
Purchase #6	$179.65	10.166%	$197.9132	$197.91	$197.90	$197.90
Purchase #7	$187.25	4.515%	$195.7043	$195.70	$195.70	$195.70
7 purchase totals =	$994.88		$1,065.3343	$1,065.33	$1,065.25	$1,065.40