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	$232.56	13.316%	$263.5277	$263.53	$263.55	$263.50
Purchase #2	$104.53	9.374%	$114.3286	$114.33	$114.35	$114.30
Purchase #3	$89.83	6.824%	$95.96	$95.96	$95.95	$96.00
Purchase #4	$99.83	3.133%	$102.9577	$102.96	$102.95	$103.00
Purchase #5	$145.49	8.753%	$158.2247	$158.22	$158.20	$158.20
Purchase #6	$250.85	12.639%	$282.5549	$282.55	$282.55	$282.60
Purchase #7	$55.26	11.614%	$61.6779	$61.68	$61.70	$61.70
7 purchase totals =	$978.35		$1,079.2315	$1,079.23	$1,079.25	$1,079.30