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	$105.96	12.541%	$119.2484	$119.25	$119.25	$119.20
Purchase #2	$165.88	11.775%	$185.4124	$185.41	$185.40	$185.40
Purchase #3	$92.82	7.450%	$99.7351	$99.74	$99.75	$99.70
Purchase #4	$234.66	10.314%	$258.8628	$258.86	$258.85	$258.90
Purchase #5	$150.76	9.570%	$165.1877	$165.19	$165.20	$165.20
Purchase #6	$104.56	4.696%	$109.4701	$109.47	$109.45	$109.50
Purchase #7	$250.55	3.131%	$258.3947	$258.39	$258.40	$258.40
7 purchase totals =	$1,105.19		$1,196.3112	$1,196.31	$1,196.30	$1,196.30