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	$187.77	4.682%	$196.5614	$196.56	$196.55	$196.60
Purchase #2	$126.34	3.113%	$130.273	$130.27	$130.25	$130.30
Purchase #3	$153.72	4.113%	$160.0425	$160.04	$160.05	$160.00
Purchase #4	$102.50	3.322%	$105.9051	$105.91	$105.90	$105.90
Purchase #5	$6.30	5.221%	$6.6289	$6.63	$6.65	$6.60
Purchase #6	$224.47	4.429%	$234.4118	$234.41	$234.40	$234.40
Purchase #7	$11.87	3.545%	$12.2908	$12.29	$12.30	$12.30
7 purchase totals =	$812.97		$846.1135	$846.11	$846.10	$846.10