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	$197.68	5.172%	$207.904	$207.90	$207.90	$207.90
Purchase #2	$31.43	12.629%	$35.3993	$35.40	$35.40	$35.40
Purchase #3	$211.72	9.647%	$232.1446	$232.14	$232.15	$232.10
Purchase #4	$112.33	9.531%	$123.0362	$123.04	$123.05	$123.00
Purchase #5	$69.35	12.496%	$78.016	$78.02	$78.00	$78.00
Purchase #6	$112.36	13.573%	$127.6106	$127.61	$127.60	$127.60
Purchase #7	$40.94	8.522%	$44.4289	$44.43	$44.45	$44.40
7 purchase totals =	$775.81		$848.5396	$848.54	$848.55	$848.40