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	$239.97	5.645%	$253.5163	$253.52	$253.50	$253.50
Purchase #2	$161.56	12.212%	$181.2897	$181.29	$181.30	$181.30
Purchase #3	$115.74	6.523%	$123.2897	$123.29	$123.30	$123.30
Purchase #4	$158.84	8.800%	$172.8179	$172.82	$172.80	$172.80
Purchase #5	$158.37	12.512%	$178.1853	$178.19	$178.20	$178.20
Purchase #6	$37.53	12.307%	$42.1488	$42.15	$42.15	$42.10
Purchase #7	$93.69	4.221%	$97.6447	$97.64	$97.65	$97.60
7 purchase totals =	$965.70		$1,048.8924	$1,048.90	$1,048.90	$1,048.80