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	$59.26	8.862%	$64.5116	$64.51	$64.50	$64.50
Purchase #2	$154.70	4.792%	$162.1132	$162.11	$162.10	$162.10
Purchase #3	$102.76	8.316%	$111.3055	$111.31	$111.30	$111.30
Purchase #4	$81.39	11.436%	$90.6978	$90.70	$90.70	$90.70
Purchase #5	$107.46	6.328%	$114.2601	$114.26	$114.25	$114.30
Purchase #6	$155.48	11.610%	$173.5312	$173.53	$173.55	$173.50
Purchase #7	$27.59	10.123%	$30.3829	$30.38	$30.40	$30.40
7 purchase totals =	$688.64		$746.8023	$746.80	$746.80	$746.80