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	$215.36	10.817%	$238.6555	$238.66	$238.65	$238.70
Purchase #2	$250.81	6.691%	$267.5917	$267.59	$267.60	$267.60
Purchase #3	$46.91	11.846%	$52.467	$52.47	$52.45	$52.50
Purchase #4	$54.29	10.132%	$59.7907	$59.79	$59.80	$59.80
Purchase #5	$206.72	5.410%	$217.9036	$217.90	$217.90	$217.90
Purchase #6	$81.64	11.502%	$91.0302	$91.03	$91.05	$91.00
Purchase #7	$68.65	7.213%	$73.6017	$73.60	$73.60	$73.60
7 purchase totals =	$924.38		$1,001.0404	$1,001.04	$1,001.05	$1,001.10