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	$142.56	13.470%	$161.7628	$161.76	$161.75	$161.80
Purchase #2	$178.40	7.582%	$191.9263	$191.93	$191.95	$191.90
Purchase #3	$205.45	5.209%	$216.1519	$216.15	$216.15	$216.20
Purchase #4	$109.65	7.630%	$118.0163	$118.02	$118.00	$118.00
Purchase #5	$127.59	3.592%	$132.173	$132.17	$132.15	$132.20
Purchase #6	$242.96	8.825%	$264.4012	$264.40	$264.40	$264.40
Purchase #7	$159.86	3.773%	$165.8915	$165.89	$165.90	$165.90
7 purchase totals =	$1,166.47		$1,250.3230	$1,250.32	$1,250.30	$1,250.40