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	$215.88	7.678%	$232.4553	$232.46	$232.45	$232.50
Purchase #2	$25.55	7.667%	$27.5089	$27.51	$27.50	$27.50
Purchase #3	$59.34	13.503%	$67.3527	$67.35	$67.35	$67.40
Purchase #4	$160.37	4.539%	$167.6492	$167.65	$167.65	$167.60
Purchase #5	$200.66	4.445%	$209.5793	$209.58	$209.60	$209.60
Purchase #6	$80.37	9.853%	$88.2889	$88.29	$88.30	$88.30
Purchase #7	$35.70	6.221%	$37.9209	$37.92	$37.90	$37.90
7 purchase totals =	$777.87		$830.7552	$830.76	$830.75	$830.80