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	$154.59	7.871%	$166.7578	$166.76	$166.75	$166.80
Purchase #2	$189.43	3.841%	$196.706	$196.71	$196.70	$196.70
Purchase #3	$147.86	13.198%	$167.3746	$167.37	$167.35	$167.40
Purchase #4	$159.71	3.804%	$165.7854	$165.79	$165.80	$165.80
Purchase #5	$172.73	8.250%	$186.9802	$186.98	$187.00	$187.00
Purchase #6	$19.48	9.110%	$21.2546	$21.25	$21.25	$21.30
Purchase #7	$52.49	6.830%	$56.0751	$56.08	$56.10	$56.10
7 purchase totals =	$896.29		$960.9337	$960.94	$960.95	$961.10