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	$136.73	4.483%	$142.8596	$142.86	$142.85	$142.90
Purchase #2	$216.27	6.304%	$229.9037	$229.90	$229.90	$229.90
Purchase #3	$36.29	6.474%	$38.6394	$38.64	$38.65	$38.60
Purchase #4	$74.61	4.566%	$78.0167	$78.02	$78.00	$78.00
Purchase #5	$62.62	8.551%	$67.9746	$67.97	$67.95	$68.00
Purchase #6	$46.37	13.620%	$52.6856	$52.69	$52.70	$52.70
Purchase #7	$130.31	4.704%	$136.4398	$136.44	$136.45	$136.40
7 purchase totals =	$703.20		$746.5194	$746.52	$746.50	$746.50