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	$212.45	11.845%	$237.6147	$237.61	$237.60	$237.60
Purchase #2	$72.32	11.147%	$80.3815	$80.38	$80.40	$80.40
Purchase #3	$46.56	5.236%	$48.9979	$49.00	$49.00	$49.00
Purchase #4	$160.93	12.821%	$181.5628	$181.56	$181.55	$181.60
Purchase #5	$85.73	10.529%	$94.7565	$94.76	$94.75	$94.80
Purchase #6	$249.34	13.253%	$282.385	$282.39	$282.40	$282.40
Purchase #7	$85.98	4.679%	$90.003	$90.00	$90.00	$90.00
7 purchase totals =	$913.31		$1,015.7014	$1,015.70	$1,015.70	$1,015.80