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	$55.25	4.844%	$57.9263	$57.93	$57.95	$57.90
Purchase #2	$71.37	9.687%	$78.2836	$78.28	$78.30	$78.30
Purchase #3	$182.89	3.424%	$189.1522	$189.15	$189.15	$189.20
Purchase #4	$161.83	10.338%	$178.56	$178.56	$178.55	$178.60
Purchase #5	$96.71	11.480%	$107.8123	$107.81	$107.80	$107.80
Purchase #6	$196.56	11.195%	$218.5649	$218.56	$218.55	$218.60
Purchase #7	$249.92	6.512%	$266.1948	$266.19	$266.20	$266.20
7 purchase totals =	$1,014.53		$1,096.4941	$1,096.48	$1,096.50	$1,096.60