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	$222.96	4.648%	$233.3232	$233.32	$233.30	$233.30
Purchase #2	$18.52	4.352%	$19.326	$19.33	$19.35	$19.30
Purchase #3	$36.65	4.455%	$38.2828	$38.28	$38.30	$38.30
Purchase #4	$174.90	3.144%	$180.3989	$180.40	$180.40	$180.40
Purchase #5	$240.73	7.364%	$258.4574	$258.46	$258.45	$258.50
Purchase #6	$146.54	5.447%	$154.522	$154.52	$154.50	$154.50
Purchase #7	$82.49	10.787%	$91.3882	$91.39	$91.40	$91.40
7 purchase totals =	$922.79		$975.6985	$975.70	$975.70	$975.70