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	$141.85	4.532%	$148.2786	$148.28	$148.30	$148.30
Purchase #2	$39.29	9.160%	$42.889	$42.89	$42.90	$42.90
Purchase #3	$242.57	12.635%	$273.2187	$273.22	$273.20	$273.20
Purchase #4	$154.48	12.220%	$173.3575	$173.36	$173.35	$173.40
Purchase #5	$186.94	4.273%	$194.9279	$194.93	$194.95	$194.90
Purchase #6	$55.75	9.764%	$61.1934	$61.19	$61.20	$61.20
Purchase #7	$224.46	9.219%	$245.153	$245.15	$245.15	$245.20
7 purchase totals =	$1,045.34		$1,139.0181	$1,139.02	$1,139.05	$1,139.10