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	$43.75	3.235%	$45.1653	$45.17	$45.15	$45.20
Purchase #2	$95.83	5.241%	$100.8525	$100.85	$100.85	$100.90
Purchase #3	$115.80	10.109%	$127.5062	$127.51	$127.50	$127.50
Purchase #4	$190.28	10.727%	$210.6913	$210.69	$210.70	$210.70
Purchase #5	$78.75	3.233%	$81.296	$81.30	$81.30	$81.30
Purchase #6	$174.31	4.627%	$182.3753	$182.38	$182.40	$182.40
Purchase #7	$85.30	10.289%	$94.0765	$94.08	$94.10	$94.10
7 purchase totals =	$784.02		$841.9631	$841.98	$842.00	$842.10