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	$84.56	5.609%	$89.303	$89.30	$89.30	$89.30
Purchase #2	$102.61	8.564%	$111.3975	$111.40	$111.40	$111.40
Purchase #3	$146.30	11.190%	$162.671	$162.67	$162.65	$162.70
Purchase #4	$157.88	13.139%	$178.6239	$178.62	$178.60	$178.60
Purchase #5	$238.52	9.758%	$261.7948	$261.79	$261.80	$261.80
Purchase #6	$154.53	9.774%	$169.6338	$169.63	$169.65	$169.60
Purchase #7	$32.98	11.812%	$36.8756	$36.88	$36.90	$36.90
7 purchase totals =	$917.38		$1,010.2996	$1,010.29	$1,010.30	$1,010.30