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	$199.46	10.866%	$221.1333	$221.13	$221.15	$221.10
Purchase #2	$52.29	6.333%	$55.6015	$55.60	$55.60	$55.60
Purchase #3	$64.71	5.534%	$68.2911	$68.29	$68.30	$68.30
Purchase #4	$19.52	6.817%	$20.8507	$20.85	$20.85	$20.90
Purchase #5	$47.33	12.414%	$53.2055	$53.21	$53.20	$53.20
Purchase #6	$210.63	5.129%	$221.4332	$221.43	$221.45	$221.40
Purchase #7	$104.63	6.297%	$111.2186	$111.22	$111.20	$111.20
7 purchase totals =	$698.57		$751.7339	$751.73	$751.75	$751.70