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	$125.40	5.118%	$131.818	$131.82	$131.80	$131.80
Purchase #2	$192.70	6.173%	$204.5954	$204.60	$204.60	$204.60
Purchase #3	$152.86	4.736%	$160.0994	$160.10	$160.10	$160.10
Purchase #4	$144.50	6.551%	$153.9662	$153.97	$153.95	$154.00
Purchase #5	$123.36	3.408%	$127.5641	$127.56	$127.55	$127.60
Purchase #6	$97.78	5.504%	$103.1618	$103.16	$103.15	$103.20
Purchase #7	$141.61	10.415%	$156.3587	$156.36	$156.35	$156.40
7 purchase totals =	$978.21		$1,037.5636	$1,037.57	$1,037.50	$1,037.70