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	$159.66	4.709%	$167.1784	$167.18	$167.20	$167.20
Purchase #2	$214.38	9.482%	$234.7075	$234.71	$234.70	$234.70
Purchase #3	$92.92	3.645%	$96.3069	$96.31	$96.30	$96.30
Purchase #4	$89.34	12.286%	$100.3163	$100.32	$100.30	$100.30
Purchase #5	$243.64	11.396%	$271.4052	$271.41	$271.40	$271.40
Purchase #6	$125.45	4.748%	$131.4064	$131.41	$131.40	$131.40
Purchase #7	$120.35	4.434%	$125.6863	$125.69	$125.70	$125.70
7 purchase totals =	$1,045.74		$1,127.0070	$1,127.03	$1,127.00	$1,127.00