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	$166.60	11.714%	$186.1155	$186.12	$186.10	$186.10
Purchase #2	$17.91	9.421%	$19.5973	$19.60	$19.60	$19.60
Purchase #3	$215.75	4.699%	$225.8881	$225.89	$225.90	$225.90
Purchase #4	$88.31	5.212%	$92.9127	$92.91	$92.90	$92.90
Purchase #5	$41.88	13.596%	$47.574	$47.57	$47.55	$47.60
Purchase #6	$172.98	5.749%	$182.9246	$182.92	$182.90	$182.90
Purchase #7	$32.53	5.506%	$34.3211	$34.32	$34.30	$34.30
7 purchase totals =	$735.96		$789.3333	$789.33	$789.25	$789.30