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	$219.51	9.503%	$240.37	$240.37	$240.35	$240.40
Purchase #2	$140.87	3.439%	$145.7145	$145.71	$145.70	$145.70
Purchase #3	$162.31	3.573%	$168.1093	$168.11	$168.10	$168.10
Purchase #4	$136.92	6.831%	$146.273	$146.27	$146.25	$146.30
Purchase #5	$209.48	12.642%	$235.9625	$235.96	$235.95	$236.00
Purchase #6	$50.82	12.353%	$57.0978	$57.10	$57.10	$57.10
Purchase #7	$98.81	8.728%	$107.4341	$107.43	$107.45	$107.40
7 purchase totals =	$1,018.72		$1,100.9612	$1,100.95	$1,100.90	$1,101.00