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	$222.76	4.495%	$232.7731	$232.77	$232.75	$232.80
Purchase #2	$56.82	5.391%	$59.8832	$59.88	$59.90	$59.90
Purchase #3	$77.88	11.379%	$86.742	$86.74	$86.75	$86.70
Purchase #4	$67.45	7.126%	$72.2565	$72.26	$72.25	$72.30
Purchase #5	$184.72	5.342%	$194.5877	$194.59	$194.60	$194.60
Purchase #6	$53.45	7.520%	$57.4694	$57.47	$57.45	$57.50
Purchase #7	$198.57	5.481%	$209.4536	$209.45	$209.45	$209.50
7 purchase totals =	$861.65		$913.1655	$913.16	$913.15	$913.30