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	$91.81	10.675%	$101.6107	$101.61	$101.60	$101.60
Purchase #2	$53.84	11.283%	$59.9148	$59.91	$59.90	$59.90
Purchase #3	$211.37	6.704%	$225.5402	$225.54	$225.55	$225.50
Purchase #4	$62.64	11.453%	$69.8142	$69.81	$69.80	$69.80
Purchase #5	$91.36	8.658%	$99.2699	$99.27	$99.25	$99.30
Purchase #6	$174.51	12.262%	$195.9084	$195.91	$195.90	$195.90
Purchase #7	$244.98	5.705%	$258.9561	$258.96	$258.95	$259.00
7 purchase totals =	$930.51		$1,011.0143	$1,011.01	$1,010.95	$1,011.00