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	$52.71	4.160%	$54.9027	$54.90	$54.90	$54.90
Purchase #2	$150.67	11.109%	$167.4079	$167.41	$167.40	$167.40
Purchase #3	$108.26	6.539%	$115.3391	$115.34	$115.35	$115.30
Purchase #4	$36.69	10.111%	$40.3997	$40.40	$40.40	$40.40
Purchase #5	$139.35	12.453%	$156.7033	$156.70	$156.70	$156.70
Purchase #6	$59.46	9.489%	$65.1022	$65.10	$65.10	$65.10
Purchase #7	$92.48	4.393%	$96.5426	$96.54	$96.55	$96.50
7 purchase totals =	$639.62		$696.3975	$696.39	$696.40	$696.30