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	$177.86	5.269%	$187.2314	$187.23	$187.25	$187.20
Purchase #2	$102.82	8.580%	$111.642	$111.64	$111.65	$111.60
Purchase #3	$152.99	4.266%	$159.5166	$159.52	$159.50	$159.50
Purchase #4	$190.56	7.866%	$205.5494	$205.55	$205.55	$205.50
Purchase #5	$231.98	3.656%	$240.4612	$240.46	$240.45	$240.50
Purchase #6	$54.73	6.797%	$58.45	$58.45	$58.45	$58.50
Purchase #7	$135.98	10.532%	$150.3014	$150.30	$150.30	$150.30
7 purchase totals =	$1,046.92		$1,113.1520	$1,113.15	$1,113.15	$1,113.10