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	$210.74	3.700%	$218.5374	$218.54	$218.55	$218.50
Purchase #2	$88.73	6.195%	$94.2268	$94.23	$94.25	$94.20
Purchase #3	$228.42	13.493%	$259.2407	$259.24	$259.25	$259.20
Purchase #4	$109.39	4.260%	$114.05	$114.05	$114.05	$114.10
Purchase #5	$102.38	4.760%	$107.2533	$107.25	$107.25	$107.30
Purchase #6	$84.75	5.284%	$89.2282	$89.23	$89.25	$89.20
Purchase #7	$210.87	8.487%	$228.7665	$228.77	$228.75	$228.80
7 purchase totals =	$1,035.28		$1,111.3029	$1,111.31	$1,111.35	$1,111.30