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	$39.75	4.747%	$41.6369	$41.64	$41.65	$41.60
Purchase #2	$240.73	5.616%	$254.2494	$254.25	$254.25	$254.20
Purchase #3	$126.58	6.864%	$135.2685	$135.27	$135.25	$135.30
Purchase #4	$238.29	12.864%	$268.9436	$268.94	$268.95	$268.90
Purchase #5	$18.89	12.151%	$21.1853	$21.19	$21.20	$21.20
Purchase #6	$186.93	6.791%	$199.6244	$199.62	$199.60	$199.60
Purchase #7	$82.56	8.383%	$89.481	$89.48	$89.50	$89.50
7 purchase totals =	$933.73		$1,010.3891	$1,010.39	$1,010.40	$1,010.30