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	$204.39	11.809%	$228.5264	$228.53	$228.55	$228.50
Purchase #2	$238.81	7.350%	$256.3625	$256.36	$256.35	$256.40
Purchase #3	$33.50	7.788%	$36.109	$36.11	$36.10	$36.10
Purchase #4	$147.72	13.628%	$167.8513	$167.85	$167.85	$167.90
Purchase #5	$149.74	12.686%	$168.736	$168.74	$168.75	$168.70
Purchase #6	$90.29	13.628%	$102.5947	$102.59	$102.60	$102.60
Purchase #7	$41.67	4.858%	$43.6943	$43.69	$43.70	$43.70
7 purchase totals =	$906.12		$1,003.8742	$1,003.87	$1,003.90	$1,003.90