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	$77.69	6.282%	$82.5705	$82.57	$82.55	$82.60
Purchase #2	$162.63	3.169%	$167.7837	$167.78	$167.80	$167.80
Purchase #3	$131.25	8.333%	$142.1871	$142.19	$142.20	$142.20
Purchase #4	$83.40	10.378%	$92.0553	$92.06	$92.05	$92.10
Purchase #5	$224.74	7.394%	$241.3573	$241.36	$241.35	$241.40
Purchase #6	$134.45	5.165%	$141.3943	$141.39	$141.40	$141.40
Purchase #7	$198.36	8.435%	$215.0917	$215.09	$215.10	$215.10
7 purchase totals =	$1,012.52		$1,082.4399	$1,082.44	$1,082.45	$1,082.60