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	$209.94	10.768%	$232.5463	$232.55	$232.55	$232.50
Purchase #2	$85.86	3.755%	$89.084	$89.08	$89.10	$89.10
Purchase #3	$75.86	10.179%	$83.5818	$83.58	$83.60	$83.60
Purchase #4	$39.30	10.194%	$43.3062	$43.31	$43.30	$43.30
Purchase #5	$137.86	3.812%	$143.1152	$143.12	$143.10	$143.10
Purchase #6	$227.62	7.535%	$244.7712	$244.77	$244.75	$244.80
Purchase #7	$179.56	4.506%	$187.651	$187.65	$187.65	$187.70
7 purchase totals =	$956.00		$1,024.0557	$1,024.06	$1,024.05	$1,024.10