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	$167.72	8.215%	$181.4982	$181.50	$181.50	$181.50
Purchase #2	$195.38	12.325%	$219.4606	$219.46	$219.45	$219.50
Purchase #3	$117.81	11.695%	$131.5879	$131.59	$131.60	$131.60
Purchase #4	$194.95	7.669%	$209.9007	$209.90	$209.90	$209.90
Purchase #5	$86.52	11.381%	$96.3668	$96.37	$96.35	$96.40
Purchase #6	$91.26	11.288%	$101.5614	$101.56	$101.55	$101.60
Purchase #7	$188.61	9.684%	$206.875	$206.88	$206.90	$206.90
7 purchase totals =	$1,042.25		$1,147.2506	$1,147.26	$1,147.25	$1,147.40