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	$223.61	4.679%	$234.0727	$234.07	$234.05	$234.10
Purchase #2	$31.50	5.507%	$33.2347	$33.23	$33.25	$33.20
Purchase #3	$73.65	11.434%	$82.0711	$82.07	$82.05	$82.10
Purchase #4	$139.64	4.734%	$146.2506	$146.25	$146.25	$146.30
Purchase #5	$69.47	13.564%	$78.8929	$78.89	$78.90	$78.90
Purchase #6	$110.97	3.544%	$114.9028	$114.90	$114.90	$114.90
Purchase #7	$150.54	12.214%	$168.927	$168.93	$168.95	$168.90
7 purchase totals =	$799.38		$858.3518	$858.34	$858.35	$858.40