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	$46.61	10.560%	$51.532	$51.53	$51.55	$51.50
Purchase #2	$158.53	5.657%	$167.498	$167.50	$167.50	$167.50
Purchase #3	$109.85	13.595%	$124.7841	$124.78	$124.80	$124.80
Purchase #4	$220.74	5.268%	$232.3686	$232.37	$232.35	$232.40
Purchase #5	$236.36	7.665%	$254.477	$254.48	$254.50	$254.50
Purchase #6	$54.44	13.447%	$61.7605	$61.76	$61.75	$61.80
Purchase #7	$175.41	12.160%	$196.7399	$196.74	$196.75	$196.70
7 purchase totals =	$1,001.94		$1,089.1601	$1,089.16	$1,089.20	$1,089.20