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	$100.56	10.138%	$110.7548	$110.75	$110.75	$110.80
Purchase #2	$232.91	4.207%	$242.7085	$242.71	$242.70	$242.70
Purchase #3	$54.61	8.294%	$59.1394	$59.14	$59.15	$59.10
Purchase #4	$200.57	10.215%	$221.0582	$221.06	$221.05	$221.10
Purchase #5	$39.42	3.693%	$40.8758	$40.88	$40.90	$40.90
Purchase #6	$205.69	7.619%	$221.3615	$221.36	$221.35	$221.40
Purchase #7	$219.99	13.129%	$248.8725	$248.87	$248.85	$248.90
7 purchase totals =	$1,053.75		$1,144.7707	$1,144.77	$1,144.75	$1,144.90