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	$106.54	3.358%	$110.1176	$110.12	$110.10	$110.10
Purchase #2	$159.71	5.670%	$168.7656	$168.77	$168.75	$168.80
Purchase #3	$137.43	5.734%	$145.3102	$145.31	$145.30	$145.30
Purchase #4	$39.66	11.853%	$44.3609	$44.36	$44.35	$44.40
Purchase #5	$139.76	10.240%	$154.0714	$154.07	$154.05	$154.10
Purchase #6	$213.33	5.462%	$224.9821	$224.98	$225.00	$225.00
Purchase #7	$215.38	10.860%	$238.7703	$238.77	$238.75	$238.80
7 purchase totals =	$1,011.81		$1,086.3781	$1,086.38	$1,086.30	$1,086.50