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	$171.71	4.369%	$179.212	$179.21	$179.20	$179.20
Purchase #2	$89.67	7.280%	$96.198	$96.20	$96.20	$96.20
Purchase #3	$147.59	13.273%	$167.1796	$167.18	$167.20	$167.20
Purchase #4	$167.59	8.749%	$182.2524	$182.25	$182.25	$182.30
Purchase #5	$76.34	13.452%	$86.6093	$86.61	$86.60	$86.60
Purchase #6	$26.98	13.126%	$30.5214	$30.52	$30.50	$30.50
Purchase #7	$80.85	12.236%	$90.7428	$90.74	$90.75	$90.70
7 purchase totals =	$760.73		$832.7155	$832.71	$832.70	$832.70