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	$57.78	3.654%	$59.8913	$59.89	$59.90	$59.90
Purchase #2	$28.66	6.410%	$30.4971	$30.50	$30.50	$30.50
Purchase #3	$201.99	4.868%	$211.8229	$211.82	$211.80	$211.80
Purchase #4	$231.72	5.251%	$243.8876	$243.89	$243.90	$243.90
Purchase #5	$50.77	3.586%	$52.5906	$52.59	$52.60	$52.60
Purchase #6	$137.99	11.284%	$153.5608	$153.56	$153.55	$153.60
Purchase #7	$11.88	4.498%	$12.4144	$12.41	$12.40	$12.40
7 purchase totals =	$720.79		$764.6647	$764.66	$764.65	$764.70