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	$69.70	8.687%	$75.7548	$75.75	$75.75	$75.80
Purchase #2	$85.36	6.472%	$90.8845	$90.88	$90.90	$90.90
Purchase #3	$196.25	9.812%	$215.5061	$215.51	$215.50	$215.50
Purchase #4	$98.93	10.403%	$109.2217	$109.22	$109.20	$109.20
Purchase #5	$98.29	6.844%	$105.017	$105.02	$105.00	$105.00
Purchase #6	$170.37	6.567%	$181.5582	$181.56	$181.55	$181.60
Purchase #7	$238.29	12.529%	$268.1454	$268.15	$268.15	$268.10
7 purchase totals =	$957.19		$1,046.0877	$1,046.09	$1,046.05	$1,046.10