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	$202.66	4.267%	$211.3075	$211.31	$211.30	$211.30
Purchase #2	$100.66	5.638%	$106.3352	$106.34	$106.35	$106.30
Purchase #3	$98.49	12.840%	$111.1361	$111.14	$111.15	$111.10
Purchase #4	$24.95	9.872%	$27.4131	$27.41	$27.40	$27.40
Purchase #5	$57.79	11.215%	$64.2711	$64.27	$64.25	$64.30
Purchase #6	$179.49	3.786%	$186.2855	$186.29	$186.30	$186.30
Purchase #7	$137.85	4.398%	$143.9126	$143.91	$143.90	$143.90
7 purchase totals =	$801.89		$850.6611	$850.67	$850.65	$850.60