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	$142.30	8.355%	$154.1892	$154.19	$154.20	$154.20
Purchase #2	$151.29	5.743%	$159.9786	$159.98	$160.00	$160.00
Purchase #3	$142.40	7.179%	$152.6229	$152.62	$152.60	$152.60
Purchase #4	$217.91	13.856%	$248.1036	$248.10	$248.10	$248.10
Purchase #5	$139.72	4.498%	$146.0046	$146.00	$146.00	$146.00
Purchase #6	$85.86	10.804%	$95.1363	$95.14	$95.15	$95.10
Purchase #7	$52.79	9.570%	$57.842	$57.84	$57.85	$57.80
7 purchase totals =	$932.27		$1,013.8772	$1,013.87	$1,013.90	$1,013.80