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	$78.66	8.273%	$85.1675	$85.17	$85.15	$85.20
Purchase #2	$193.51	6.704%	$206.4829	$206.48	$206.50	$206.50
Purchase #3	$243.57	12.449%	$273.892	$273.89	$273.90	$273.90
Purchase #4	$88.83	12.437%	$99.8778	$99.88	$99.90	$99.90
Purchase #5	$205.82	8.349%	$223.0039	$223.00	$223.00	$223.00
Purchase #6	$238.48	7.157%	$255.548	$255.55	$255.55	$255.50
Purchase #7	$61.38	3.292%	$63.4006	$63.40	$63.40	$63.40
7 purchase totals =	$1,110.25		$1,207.3727	$1,207.37	$1,207.40	$1,207.40