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	$94.46	4.813%	$99.0064	$99.01	$99.00	$99.00
Purchase #2	$97.84	5.715%	$103.4316	$103.43	$103.45	$103.40
Purchase #3	$190.33	8.479%	$206.4681	$206.47	$206.45	$206.50
Purchase #4	$13.41	10.454%	$14.8119	$14.81	$14.80	$14.80
Purchase #5	$96.53	6.830%	$103.123	$103.12	$103.10	$103.10
Purchase #6	$227.25	9.278%	$248.3343	$248.33	$248.35	$248.30
Purchase #7	$228.88	6.204%	$243.0797	$243.08	$243.10	$243.10
7 purchase totals =	$948.70		$1,018.2550	$1,018.25	$1,018.25	$1,018.20