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	$113.26	11.418%	$126.192	$126.19	$126.20	$126.20
Purchase #2	$49.91	6.834%	$53.3208	$53.32	$53.30	$53.30
Purchase #3	$154.46	12.840%	$174.2927	$174.29	$174.30	$174.30
Purchase #4	$81.49	10.211%	$89.8109	$89.81	$89.80	$89.80
Purchase #5	$70.83	7.249%	$75.9645	$75.96	$75.95	$76.00
Purchase #6	$116.49	9.705%	$127.7954	$127.80	$127.80	$127.80
Purchase #7	$249.60	12.424%	$280.6103	$280.61	$280.60	$280.60
7 purchase totals =	$836.04		$927.9866	$927.98	$927.95	$928.00