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	$149.28	6.245%	$158.6025	$158.60	$158.60	$158.60
Purchase #2	$70.66	3.171%	$72.9006	$72.90	$72.90	$72.90
Purchase #3	$106.60	4.300%	$111.1838	$111.18	$111.20	$111.20
Purchase #4	$116.83	7.279%	$125.3341	$125.33	$125.35	$125.30
Purchase #5	$153.36	6.166%	$162.8162	$162.82	$162.80	$162.80
Purchase #6	$167.63	9.397%	$183.3822	$183.38	$183.40	$183.40
Purchase #7	$80.48	7.481%	$86.5007	$86.50	$86.50	$86.50
7 purchase totals =	$844.84		$900.7201	$900.71	$900.75	$900.70