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	$52.75	8.224%	$57.0882	$57.09	$57.10	$57.10
Purchase #2	$168.53	6.314%	$179.171	$179.17	$179.15	$179.20
Purchase #3	$101.53	13.588%	$115.3259	$115.33	$115.35	$115.30
Purchase #4	$169.51	7.644%	$182.4673	$182.47	$182.45	$182.50
Purchase #5	$244.90	9.596%	$268.4006	$268.40	$268.40	$268.40
Purchase #6	$47.28	11.779%	$52.8491	$52.85	$52.85	$52.80
Purchase #7	$224.28	11.732%	$250.5925	$250.59	$250.60	$250.60
7 purchase totals =	$1,008.78		$1,105.8946	$1,105.90	$1,105.90	$1,105.90