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	$125.87	4.516%	$131.5543	$131.55	$131.55	$131.60
Purchase #2	$223.86	8.369%	$242.5948	$242.59	$242.60	$242.60
Purchase #3	$171.49	4.624%	$179.4197	$179.42	$179.40	$179.40
Purchase #4	$171.50	8.814%	$186.616	$186.62	$186.60	$186.60
Purchase #5	$11.71	6.289%	$12.4464	$12.45	$12.45	$12.40
Purchase #6	$213.57	4.650%	$223.501	$223.50	$223.50	$223.50
Purchase #7	$122.32	4.225%	$127.488	$127.49	$127.50	$127.50
7 purchase totals =	$1,040.32		$1,103.6202	$1,103.62	$1,103.60	$1,103.60