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	$249.76	10.431%	$275.8125	$275.81	$275.80	$275.80
Purchase #2	$101.67	11.693%	$113.5583	$113.56	$113.55	$113.60
Purchase #3	$110.42	7.842%	$119.0791	$119.08	$119.10	$119.10
Purchase #4	$92.67	13.263%	$104.9608	$104.96	$104.95	$105.00
Purchase #5	$77.96	11.442%	$86.8802	$86.88	$86.90	$86.90
Purchase #6	$175.91	11.631%	$196.3701	$196.37	$196.35	$196.40
Purchase #7	$141.46	5.157%	$148.7551	$148.76	$148.75	$148.80
7 purchase totals =	$949.85		$1,045.4161	$1,045.42	$1,045.40	$1,045.60