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	$116.79	5.479%	$123.1889	$123.19	$123.20	$123.20
Purchase #2	$96.71	13.705%	$109.9641	$109.96	$109.95	$110.00
Purchase #3	$168.61	6.654%	$179.8293	$179.83	$179.85	$179.80
Purchase #4	$43.48	8.799%	$47.3058	$47.31	$47.30	$47.30
Purchase #5	$197.48	6.532%	$210.3794	$210.38	$210.40	$210.40
Purchase #6	$61.52	8.784%	$66.9239	$66.92	$66.90	$66.90
Purchase #7	$241.85	9.611%	$265.0942	$265.09	$265.10	$265.10
7 purchase totals =	$926.44		$1,002.6856	$1,002.68	$1,002.70	$1,002.70