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	$174.62	12.542%	$196.5208	$196.52	$196.50	$196.50
Purchase #2	$138.93	3.708%	$144.0815	$144.08	$144.10	$144.10
Purchase #3	$71.92	3.685%	$74.5703	$74.57	$74.55	$74.60
Purchase #4	$27.44	9.191%	$29.962	$29.96	$29.95	$30.00
Purchase #5	$73.36	11.567%	$81.8456	$81.85	$81.85	$81.80
Purchase #6	$128.76	4.720%	$134.8375	$134.84	$134.85	$134.80
Purchase #7	$82.40	10.303%	$90.8897	$90.89	$90.90	$90.90
7 purchase totals =	$697.43		$752.7074	$752.71	$752.70	$752.70