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	$85.27	6.603%	$90.9004	$90.90	$90.90	$90.90
Purchase #2	$206.37	3.696%	$213.9974	$214.00	$214.00	$214.00
Purchase #3	$114.77	8.369%	$124.3751	$124.38	$124.40	$124.40
Purchase #4	$234.27	3.201%	$241.769	$241.77	$241.75	$241.80
Purchase #5	$5.30	10.849%	$5.875	$5.88	$5.90	$5.90
Purchase #6	$125.39	13.729%	$142.6048	$142.60	$142.60	$142.60
Purchase #7	$170.68	11.736%	$190.711	$190.71	$190.70	$190.70
7 purchase totals =	$942.05		$1,010.2327	$1,010.24	$1,010.25	$1,010.30