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	$224.52	4.109%	$233.7455	$233.75	$233.75	$233.70
Purchase #2	$238.78	8.405%	$258.8495	$258.85	$258.85	$258.80
Purchase #3	$50.59	4.798%	$53.0173	$53.02	$53.00	$53.00
Purchase #4	$114.54	12.227%	$128.5448	$128.54	$128.55	$128.50
Purchase #5	$184.77	13.480%	$209.677	$209.68	$209.70	$209.70
Purchase #6	$93.92	3.424%	$97.1358	$97.14	$97.15	$97.10
Purchase #7	$107.65	11.365%	$119.8844	$119.88	$119.90	$119.90
7 purchase totals =	$1,014.77		$1,100.8543	$1,100.86	$1,100.90	$1,100.70