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	$59.52	8.500%	$64.5792	$64.58	$64.60	$64.60
Purchase #2	$215.70	3.502%	$223.2538	$223.25	$223.25	$223.30
Purchase #3	$173.75	4.181%	$181.0145	$181.01	$181.00	$181.00
Purchase #4	$172.65	9.424%	$188.9205	$188.92	$188.90	$188.90
Purchase #5	$155.66	8.364%	$168.6794	$168.68	$168.70	$168.70
Purchase #6	$120.31	3.831%	$124.9191	$124.92	$124.90	$124.90
Purchase #7	$210.98	11.151%	$234.5064	$234.51	$234.50	$234.50
7 purchase totals =	$1,108.57		$1,185.8729	$1,185.87	$1,185.85	$1,185.90