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	$49.80	8.692%	$54.1286	$54.13	$54.15	$54.10
Purchase #2	$119.78	8.632%	$130.1194	$130.12	$130.10	$130.10
Purchase #3	$90.31	6.188%	$95.8984	$95.90	$95.90	$95.90
Purchase #4	$236.52	4.558%	$247.3006	$247.30	$247.30	$247.30
Purchase #5	$171.46	13.423%	$194.4751	$194.48	$194.50	$194.50
Purchase #6	$78.93	7.508%	$84.8561	$84.86	$84.85	$84.90
Purchase #7	$72.78	10.658%	$80.5369	$80.54	$80.55	$80.50
7 purchase totals =	$819.58		$887.3151	$887.33	$887.35	$887.30