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	$196.76	4.535%	$205.6831	$205.68	$205.70	$205.70
Purchase #2	$174.85	12.311%	$196.3758	$196.38	$196.40	$196.40
Purchase #3	$150.67	11.278%	$167.6626	$167.66	$167.65	$167.70
Purchase #4	$20.41	6.109%	$21.6568	$21.66	$21.65	$21.70
Purchase #5	$17.47	12.399%	$19.6361	$19.64	$19.65	$19.60
Purchase #6	$111.33	11.682%	$124.3356	$124.34	$124.35	$124.30
Purchase #7	$79.92	3.519%	$82.7324	$82.73	$82.75	$82.70
7 purchase totals =	$751.41		$818.0824	$818.09	$818.15	$818.10