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	$127.96	4.865%	$134.1853	$134.19	$134.20	$134.20
Purchase #2	$164.77	4.333%	$171.9095	$171.91	$171.90	$171.90
Purchase #3	$230.64	3.574%	$238.8831	$238.88	$238.90	$238.90
Purchase #4	$116.84	12.663%	$131.6354	$131.64	$131.65	$131.60
Purchase #5	$43.48	4.784%	$45.5601	$45.56	$45.55	$45.60
Purchase #6	$166.33	13.236%	$188.3454	$188.35	$188.35	$188.30
Purchase #7	$42.80	7.280%	$45.9158	$45.92	$45.90	$45.90
7 purchase totals =	$892.82		$956.4346	$956.45	$956.45	$956.40