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	$178.97	6.173%	$190.0178	$190.02	$190.00	$190.00
Purchase #2	$97.28	8.492%	$105.541	$105.54	$105.55	$105.50
Purchase #3	$32.42	12.274%	$36.3992	$36.40	$36.40	$36.40
Purchase #4	$183.26	4.158%	$190.88	$190.88	$190.90	$190.90
Purchase #5	$133.47	11.108%	$148.2958	$148.30	$148.30	$148.30
Purchase #6	$60.66	10.649%	$67.1197	$67.12	$67.10	$67.10
Purchase #7	$10.97	5.345%	$11.5563	$11.56	$11.55	$11.60
7 purchase totals =	$697.03		$749.8098	$749.82	$749.80	$749.80