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	$94.33	3.465%	$97.5985	$97.60	$97.60	$97.60
Purchase #2	$136.41	10.409%	$150.6089	$150.61	$150.60	$150.60
Purchase #3	$155.89	7.145%	$167.0283	$167.03	$167.05	$167.00
Purchase #4	$209.92	13.487%	$238.2319	$238.23	$238.25	$238.20
Purchase #5	$240.96	9.755%	$264.4656	$264.47	$264.45	$264.50
Purchase #6	$117.31	5.354%	$123.5908	$123.59	$123.60	$123.60
Purchase #7	$210.57	10.706%	$233.1136	$233.11	$233.10	$233.10
7 purchase totals =	$1,165.39		$1,274.6376	$1,274.64	$1,274.65	$1,274.60