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	$221.94	10.857%	$246.036	$246.04	$246.05	$246.00
Purchase #2	$162.26	10.600%	$179.4596	$179.46	$179.45	$179.50
Purchase #3	$112.75	12.702%	$127.0715	$127.07	$127.05	$127.10
Purchase #4	$160.96	3.524%	$166.6322	$166.63	$166.65	$166.60
Purchase #5	$193.42	8.564%	$209.9845	$209.98	$210.00	$210.00
Purchase #6	$138.86	5.773%	$146.8764	$146.88	$146.90	$146.90
Purchase #7	$68.50	11.437%	$76.3343	$76.33	$76.35	$76.30
7 purchase totals =	$1,058.69		$1,152.3945	$1,152.39	$1,152.45	$1,152.40