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	$168.71	4.501%	$176.3036	$176.30	$176.30	$176.30
Purchase #2	$29.80	12.574%	$33.5471	$33.55	$33.55	$33.50
Purchase #3	$193.87	11.174%	$215.533	$215.53	$215.55	$215.50
Purchase #4	$135.29	6.436%	$143.9973	$144.00	$144.00	$144.00
Purchase #5	$6.57	11.482%	$7.3244	$7.32	$7.30	$7.30
Purchase #6	$67.41	4.178%	$70.2264	$70.23	$70.25	$70.20
Purchase #7	$70.55	10.758%	$78.1398	$78.14	$78.15	$78.10
7 purchase totals =	$672.20		$725.0716	$725.07	$725.10	$724.90