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	$161.71	3.504%	$167.3763	$167.38	$167.40	$167.40
Purchase #2	$164.88	12.478%	$185.4537	$185.45	$185.45	$185.50
Purchase #3	$233.87	3.863%	$242.9044	$242.90	$242.90	$242.90
Purchase #4	$49.99	10.524%	$55.2509	$55.25	$55.25	$55.30
Purchase #5	$108.77	3.374%	$112.4399	$112.44	$112.45	$112.40
Purchase #6	$75.95	13.637%	$86.3073	$86.31	$86.30	$86.30
Purchase #7	$115.54	7.436%	$124.1316	$124.13	$124.15	$124.10
7 purchase totals =	$910.71		$973.8641	$973.86	$973.90	$973.90