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	$95.63	5.333%	$100.7299	$100.73	$100.75	$100.70
Purchase #2	$67.89	6.262%	$72.1413	$72.14	$72.15	$72.10
Purchase #3	$170.32	6.346%	$181.1285	$181.13	$181.15	$181.10
Purchase #4	$123.53	5.845%	$130.7503	$130.75	$130.75	$130.80
Purchase #5	$164.61	4.507%	$172.029	$172.03	$172.05	$172.00
Purchase #6	$8.69	6.644%	$9.2674	$9.27	$9.25	$9.30
Purchase #7	$170.85	6.709%	$182.3123	$182.31	$182.30	$182.30
7 purchase totals =	$801.52		$848.3587	$848.36	$848.40	$848.30