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	$151.67	8.419%	$164.4391	$164.44	$164.45	$164.40
Purchase #2	$194.59	12.655%	$219.2154	$219.22	$219.20	$219.20
Purchase #3	$79.69	3.715%	$82.6505	$82.65	$82.65	$82.70
Purchase #4	$131.40	6.225%	$139.5797	$139.58	$139.60	$139.60
Purchase #5	$6.91	6.786%	$7.3789	$7.38	$7.40	$7.40
Purchase #6	$59.35	3.126%	$61.2053	$61.21	$61.20	$61.20
Purchase #7	$246.87	8.751%	$268.4736	$268.47	$268.45	$268.50
7 purchase totals =	$870.48		$942.9425	$942.95	$942.95	$943.00