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	$196.29	6.406%	$208.8643	$208.86	$208.85	$208.90
Purchase #2	$154.68	10.158%	$170.3924	$170.39	$170.40	$170.40
Purchase #3	$79.87	10.579%	$88.3194	$88.32	$88.30	$88.30
Purchase #4	$174.73	12.323%	$196.262	$196.26	$196.25	$196.30
Purchase #5	$173.26	10.413%	$191.3016	$191.30	$191.30	$191.30
Purchase #6	$45.95	11.764%	$51.3556	$51.36	$51.35	$51.40
Purchase #7	$175.29	6.869%	$187.3307	$187.33	$187.35	$187.30
7 purchase totals =	$1,000.07		$1,093.8260	$1,093.82	$1,093.80	$1,093.90