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	$35.26	7.319%	$37.8407	$37.84	$37.85	$37.80
Purchase #2	$151.41	7.814%	$163.2412	$163.24	$163.25	$163.20
Purchase #3	$77.60	6.410%	$82.5742	$82.57	$82.55	$82.60
Purchase #4	$5.31	11.538%	$5.9227	$5.92	$5.90	$5.90
Purchase #5	$91.72	7.835%	$98.9063	$98.91	$98.90	$98.90
Purchase #6	$73.72	12.168%	$82.6902	$82.69	$82.70	$82.70
Purchase #7	$133.29	4.860%	$139.7679	$139.77	$139.75	$139.80
7 purchase totals =	$568.31		$610.9432	$610.94	$610.90	$610.90