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	$94.82	4.375%	$98.9684	$98.97	$98.95	$99.00
Purchase #2	$79.65	5.195%	$83.7878	$83.79	$83.80	$83.80
Purchase #3	$247.56	5.407%	$260.9456	$260.95	$260.95	$260.90
Purchase #4	$76.35	12.849%	$86.1602	$86.16	$86.15	$86.20
Purchase #5	$100.94	10.272%	$111.3086	$111.31	$111.30	$111.30
Purchase #6	$54.83	8.552%	$59.5191	$59.52	$59.50	$59.50
Purchase #7	$127.75	12.782%	$144.079	$144.08	$144.10	$144.10
7 purchase totals =	$781.90		$844.7687	$844.78	$844.75	$844.80