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	$172.68	6.759%	$184.3514	$184.35	$184.35	$184.40
Purchase #2	$206.54	6.330%	$219.614	$219.61	$219.60	$219.60
Purchase #3	$178.59	12.361%	$200.6655	$200.67	$200.65	$200.70
Purchase #4	$52.81	12.151%	$59.2269	$59.23	$59.25	$59.20
Purchase #5	$56.96	13.322%	$64.5482	$64.55	$64.55	$64.50
Purchase #6	$104.86	13.801%	$119.3317	$119.33	$119.35	$119.30
Purchase #7	$149.54	12.721%	$168.563	$168.56	$168.55	$168.60
7 purchase totals =	$921.98		$1,016.3007	$1,016.30	$1,016.30	$1,016.30