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	$119.72	12.717%	$134.9448	$134.94	$134.95	$134.90
Purchase #2	$81.76	5.770%	$86.4776	$86.48	$86.50	$86.50
Purchase #3	$75.78	3.441%	$78.3876	$78.39	$78.40	$78.40
Purchase #4	$104.95	9.231%	$114.6379	$114.64	$114.65	$114.60
Purchase #5	$61.33	10.472%	$67.7525	$67.75	$67.75	$67.80
Purchase #6	$244.37	9.771%	$268.2474	$268.25	$268.25	$268.20
Purchase #7	$161.92	13.625%	$183.9816	$183.98	$184.00	$184.00
7 purchase totals =	$849.83		$934.4294	$934.43	$934.50	$934.40