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	$203.96	9.784%	$223.9154	$223.92	$223.90	$223.90
Purchase #2	$102.93	10.848%	$114.0958	$114.10	$114.10	$114.10
Purchase #3	$78.37	4.747%	$82.0902	$82.09	$82.10	$82.10
Purchase #4	$230.90	8.155%	$249.7299	$249.73	$249.75	$249.70
Purchase #5	$98.62	10.616%	$109.0895	$109.09	$109.10	$109.10
Purchase #6	$244.73	11.850%	$273.7305	$273.73	$273.75	$273.70
Purchase #7	$43.81	8.746%	$47.6416	$47.64	$47.65	$47.60
7 purchase totals =	$1,003.32		$1,100.2929	$1,100.30	$1,100.35	$1,100.20