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	$230.36	13.473%	$261.3964	$261.40	$261.40	$261.40
Purchase #2	$128.30	8.776%	$139.5596	$139.56	$139.55	$139.60
Purchase #3	$131.51	11.412%	$146.5179	$146.52	$146.50	$146.50
Purchase #4	$90.59	6.546%	$96.52	$96.52	$96.50	$96.50
Purchase #5	$77.97	13.614%	$88.5848	$88.58	$88.60	$88.60
Purchase #6	$152.43	6.466%	$162.2861	$162.29	$162.30	$162.30
Purchase #7	$114.79	5.663%	$121.2906	$121.29	$121.30	$121.30
7 purchase totals =	$925.95		$1,016.1554	$1,016.16	$1,016.15	$1,016.20