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	$139.71	8.332%	$151.3506	$151.35	$151.35	$151.40
Purchase #2	$33.69	4.251%	$35.1222	$35.12	$35.10	$35.10
Purchase #3	$122.94	3.332%	$127.0364	$127.04	$127.05	$127.00
Purchase #4	$180.57	8.719%	$196.3139	$196.31	$196.30	$196.30
Purchase #5	$240.88	8.582%	$261.5523	$261.55	$261.55	$261.60
Purchase #6	$13.45	10.781%	$14.9	$14.90	$14.90	$14.90
Purchase #7	$207.55	3.439%	$214.6876	$214.69	$214.70	$214.70
7 purchase totals =	$938.79		$1,000.9630	$1,000.96	$1,000.95	$1,001.00