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	$93.43	3.355%	$96.5646	$96.56	$96.55	$96.60
Purchase #2	$92.58	11.813%	$103.5165	$103.52	$103.50	$103.50
Purchase #3	$217.61	9.599%	$238.4984	$238.50	$238.50	$238.50
Purchase #4	$86.36	11.701%	$96.465	$96.47	$96.45	$96.50
Purchase #5	$234.56	7.190%	$251.4249	$251.42	$251.40	$251.40
Purchase #6	$60.63	9.687%	$66.5032	$66.50	$66.50	$66.50
Purchase #7	$219.92	3.280%	$227.1334	$227.13	$227.15	$227.10
7 purchase totals =	$1,005.09		$1,080.1060	$1,080.10	$1,080.05	$1,080.10