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	$232.89	5.326%	$245.2937	$245.29	$245.30	$245.30
Purchase #2	$99.30	9.861%	$109.092	$109.09	$109.10	$109.10
Purchase #3	$134.30	4.524%	$140.3757	$140.38	$140.40	$140.40
Purchase #4	$110.65	10.151%	$121.8821	$121.88	$121.90	$121.90
Purchase #5	$153.83	12.833%	$173.571	$173.57	$173.55	$173.60
Purchase #6	$33.51	10.676%	$37.0875	$37.09	$37.10	$37.10
Purchase #7	$191.90	9.433%	$210.0019	$210.00	$210.00	$210.00
7 purchase totals =	$956.38		$1,037.3039	$1,037.30	$1,037.35	$1,037.40