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	$49.69	12.286%	$55.7949	$55.79	$55.80	$55.80
Purchase #2	$205.69	7.481%	$221.0777	$221.08	$221.10	$221.10
Purchase #3	$116.56	3.248%	$120.3459	$120.35	$120.35	$120.30
Purchase #4	$72.43	7.861%	$78.1237	$78.12	$78.10	$78.10
Purchase #5	$90.35	6.461%	$96.1875	$96.19	$96.20	$96.20
Purchase #6	$95.59	5.788%	$101.1227	$101.12	$101.10	$101.10
Purchase #7	$55.61	7.441%	$59.7479	$59.75	$59.75	$59.70
7 purchase totals =	$685.92		$732.4003	$732.40	$732.40	$732.30