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	$88.87	4.530%	$92.8958	$92.90	$92.90	$92.90
Purchase #2	$238.28	12.114%	$267.1452	$267.15	$267.15	$267.10
Purchase #3	$47.37	9.630%	$51.9317	$51.93	$51.95	$51.90
Purchase #4	$57.94	5.637%	$61.2061	$61.21	$61.20	$61.20
Purchase #5	$105.66	5.458%	$111.4269	$111.43	$111.45	$111.40
Purchase #6	$101.91	7.314%	$109.3637	$109.36	$109.35	$109.40
Purchase #7	$35.93	6.579%	$38.2938	$38.29	$38.30	$38.30
7 purchase totals =	$675.96		$732.2632	$732.27	$732.30	$732.20