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	$35.41	5.393%	$37.3197	$37.32	$37.30	$37.30
Purchase #2	$115.49	13.499%	$131.08	$131.08	$131.10	$131.10
Purchase #3	$83.33	5.237%	$87.694	$87.69	$87.70	$87.70
Purchase #4	$61.56	9.571%	$67.4519	$67.45	$67.45	$67.50
Purchase #5	$88.98	6.160%	$94.4612	$94.46	$94.45	$94.50
Purchase #6	$151.76	7.112%	$162.5532	$162.55	$162.55	$162.60
Purchase #7	$185.32	11.429%	$206.5002	$206.50	$206.50	$206.50
7 purchase totals =	$721.85		$787.0602	$787.05	$787.05	$787.20