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	$44.67	6.688%	$47.6575	$47.66	$47.65	$47.70
Purchase #2	$32.28	4.708%	$33.7997	$33.80	$33.80	$33.80
Purchase #3	$189.42	6.709%	$202.1282	$202.13	$202.15	$202.10
Purchase #4	$99.89	9.222%	$109.1019	$109.10	$109.10	$109.10
Purchase #5	$101.46	9.711%	$111.3128	$111.31	$111.30	$111.30
Purchase #6	$19.93	9.712%	$21.8656	$21.87	$21.85	$21.90
Purchase #7	$156.67	8.414%	$169.8522	$169.85	$169.85	$169.90
7 purchase totals =	$644.32		$695.7179	$695.72	$695.70	$695.80