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	$183.94	3.498%	$190.3742	$190.37	$190.35	$190.40
Purchase #2	$126.58	5.704%	$133.8001	$133.80	$133.80	$133.80
Purchase #3	$146.49	11.182%	$162.8705	$162.87	$162.85	$162.90
Purchase #4	$134.46	12.162%	$150.813	$150.81	$150.80	$150.80
Purchase #5	$73.59	12.374%	$82.696	$82.70	$82.70	$82.70
Purchase #6	$117.88	7.832%	$127.1124	$127.11	$127.10	$127.10
Purchase #7	$30.98	8.747%	$33.6898	$33.69	$33.70	$33.70
7 purchase totals =	$813.92		$881.3560	$881.35	$881.30	$881.40