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	$32.45	13.522%	$36.8379	$36.84	$36.85	$36.80
Purchase #2	$107.74	8.485%	$116.8817	$116.88	$116.90	$116.90
Purchase #3	$171.26	11.371%	$190.734	$190.73	$190.75	$190.70
Purchase #4	$56.63	13.592%	$64.3271	$64.33	$64.35	$64.30
Purchase #5	$172.69	8.354%	$187.1165	$187.12	$187.10	$187.10
Purchase #6	$218.31	9.262%	$238.5299	$238.53	$238.55	$238.50
Purchase #7	$172.87	3.330%	$178.6266	$178.63	$178.65	$178.60
7 purchase totals =	$931.95		$1,013.0537	$1,013.06	$1,013.15	$1,012.90