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	$198.82	6.835%	$212.4093	$212.41	$212.40	$212.40
Purchase #2	$164.80	11.589%	$183.8987	$183.90	$183.90	$183.90
Purchase #3	$232.29	4.432%	$242.5851	$242.59	$242.60	$242.60
Purchase #4	$65.92	9.684%	$72.3037	$72.30	$72.30	$72.30
Purchase #5	$164.77	4.599%	$172.3478	$172.35	$172.35	$172.30
Purchase #6	$89.61	11.234%	$99.6768	$99.68	$99.70	$99.70
Purchase #7	$38.29	7.865%	$41.3015	$41.30	$41.30	$41.30
7 purchase totals =	$954.50		$1,024.5229	$1,024.53	$1,024.55	$1,024.50