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	$35.98	5.573%	$37.9852	$37.99	$38.00	$38.00
Purchase #2	$62.84	4.391%	$65.5993	$65.60	$65.60	$65.60
Purchase #3	$28.69	7.644%	$30.8831	$30.88	$30.90	$30.90
Purchase #4	$106.86	9.117%	$116.6024	$116.60	$116.60	$116.60
Purchase #5	$25.61	9.713%	$28.0975	$28.10	$28.10	$28.10
Purchase #6	$174.83	12.238%	$196.2257	$196.23	$196.25	$196.20
Purchase #7	$44.65	4.109%	$46.4847	$46.48	$46.50	$46.50
7 purchase totals =	$479.46		$521.8779	$521.88	$521.95	$521.90