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	$46.86	11.648%	$52.3183	$52.32	$52.30	$52.30
Purchase #2	$25.90	9.809%	$28.4405	$28.44	$28.45	$28.40
Purchase #3	$196.43	12.862%	$221.6948	$221.69	$221.70	$221.70
Purchase #4	$218.50	7.381%	$234.6275	$234.63	$234.65	$234.60
Purchase #5	$223.67	6.217%	$237.5756	$237.58	$237.60	$237.60
Purchase #6	$117.48	13.577%	$133.4303	$133.43	$133.45	$133.40
Purchase #7	$185.54	5.844%	$196.383	$196.38	$196.40	$196.40
7 purchase totals =	$1,014.38		$1,104.4700	$1,104.47	$1,104.55	$1,104.40