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	$248.51	6.166%	$263.8331	$263.83	$263.85	$263.80
Purchase #2	$54.61	6.792%	$58.3191	$58.32	$58.30	$58.30
Purchase #3	$169.28	6.119%	$179.6382	$179.64	$179.65	$179.60
Purchase #4	$81.33	11.151%	$90.3991	$90.40	$90.40	$90.40
Purchase #5	$180.50	3.193%	$186.2634	$186.26	$186.25	$186.30
Purchase #6	$47.45	12.521%	$53.3912	$53.39	$53.40	$53.40
Purchase #7	$161.92	10.121%	$178.3079	$178.31	$178.30	$178.30
7 purchase totals =	$943.60		$1,010.1520	$1,010.15	$1,010.15	$1,010.10