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	$93.31	10.312%	$102.9321	$102.93	$102.95	$102.90
Purchase #2	$73.41	8.407%	$79.5816	$79.58	$79.60	$79.60
Purchase #3	$188.74	4.314%	$196.8822	$196.88	$196.90	$196.90
Purchase #4	$123.60	3.840%	$128.3462	$128.35	$128.35	$128.30
Purchase #5	$223.53	7.206%	$239.6376	$239.64	$239.65	$239.60
Purchase #6	$97.26	3.253%	$100.4239	$100.42	$100.40	$100.40
Purchase #7	$250.90	11.427%	$279.5703	$279.57	$279.55	$279.60
7 purchase totals =	$1,050.75		$1,127.3739	$1,127.37	$1,127.40	$1,127.30