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	$80.89	5.709%	$85.508	$85.51	$85.50	$85.50
Purchase #2	$58.30	7.745%	$62.8153	$62.82	$62.80	$62.80
Purchase #3	$217.73	7.159%	$233.3173	$233.32	$233.30	$233.30
Purchase #4	$101.70	4.537%	$106.3141	$106.31	$106.30	$106.30
Purchase #5	$188.47	11.506%	$210.1554	$210.16	$210.15	$210.20
Purchase #6	$95.77	8.559%	$103.967	$103.97	$103.95	$104.00
Purchase #7	$130.91	8.614%	$142.1866	$142.19	$142.20	$142.20
7 purchase totals =	$873.77		$944.2637	$944.28	$944.20	$944.30