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	$135.52	7.480%	$145.6569	$145.66	$145.65	$145.70
Purchase #2	$150.48	10.229%	$165.8726	$165.87	$165.85	$165.90
Purchase #3	$191.77	11.469%	$213.7641	$213.76	$213.75	$213.80
Purchase #4	$67.74	4.560%	$70.8289	$70.83	$70.85	$70.80
Purchase #5	$145.83	3.830%	$151.4153	$151.42	$151.40	$151.40
Purchase #6	$92.58	3.675%	$95.9823	$95.98	$96.00	$96.00
Purchase #7	$213.43	9.314%	$233.3089	$233.31	$233.30	$233.30
7 purchase totals =	$997.35		$1,076.8290	$1,076.83	$1,076.80	$1,076.90