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	$54.68	13.177%	$61.8852	$61.89	$61.90	$61.90
Purchase #2	$217.90	7.512%	$234.2686	$234.27	$234.25	$234.30
Purchase #3	$92.59	12.298%	$103.9767	$103.98	$104.00	$104.00
Purchase #4	$237.90	9.824%	$261.2713	$261.27	$261.25	$261.30
Purchase #5	$57.62	9.172%	$62.9049	$62.90	$62.90	$62.90
Purchase #6	$213.43	12.567%	$240.2517	$240.25	$240.25	$240.30
Purchase #7	$94.25	6.524%	$100.3989	$100.40	$100.40	$100.40
7 purchase totals =	$968.37		$1,064.9573	$1,064.96	$1,064.95	$1,065.10