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	$96.98	4.729%	$101.5662	$101.57	$101.55	$101.60
Purchase #2	$158.76	9.558%	$173.9343	$173.93	$173.95	$173.90
Purchase #3	$178.98	7.334%	$192.1064	$192.11	$192.10	$192.10
Purchase #4	$41.37	3.308%	$42.7385	$42.74	$42.75	$42.70
Purchase #5	$78.69	4.827%	$82.4884	$82.49	$82.50	$82.50
Purchase #6	$226.49	9.131%	$247.1708	$247.17	$247.15	$247.20
Purchase #7	$242.45	12.175%	$271.9683	$271.97	$271.95	$272.00
7 purchase totals =	$1,023.72		$1,111.9729	$1,111.98	$1,111.95	$1,112.00