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	$41.31	5.659%	$43.6477	$43.65	$43.65	$43.60
Purchase #2	$249.32	3.623%	$258.3529	$258.35	$258.35	$258.40
Purchase #3	$58.46	10.374%	$64.5246	$64.52	$64.50	$64.50
Purchase #4	$163.77	11.218%	$182.1417	$182.14	$182.15	$182.10
Purchase #5	$188.82	13.797%	$214.8715	$214.87	$214.85	$214.90
Purchase #6	$208.60	6.779%	$222.741	$222.74	$222.75	$222.70
Purchase #7	$30.72	9.133%	$33.5257	$33.53	$33.55	$33.50
7 purchase totals =	$941.00		$1,019.8051	$1,019.80	$1,019.80	$1,019.70