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	$166.72	7.150%	$178.6405	$178.64	$178.65	$178.60
Purchase #2	$153.76	5.546%	$162.2875	$162.29	$162.30	$162.30
Purchase #3	$142.66	6.670%	$152.1754	$152.18	$152.20	$152.20
Purchase #4	$84.76	12.367%	$95.2423	$95.24	$95.25	$95.20
Purchase #5	$214.69	9.864%	$235.867	$235.87	$235.85	$235.90
Purchase #6	$37.84	13.472%	$42.9378	$42.94	$42.95	$42.90
Purchase #7	$128.56	5.192%	$135.2348	$135.23	$135.25	$135.20
7 purchase totals =	$928.99		$1,002.3853	$1,002.39	$1,002.45	$1,002.30