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	$131.34	7.529%	$141.2286	$141.23	$141.25	$141.20
Purchase #2	$106.76	4.358%	$111.4126	$111.41	$111.40	$111.40
Purchase #3	$148.98	10.551%	$164.6989	$164.70	$164.70	$164.70
Purchase #4	$40.27	9.219%	$43.9825	$43.98	$44.00	$44.00
Purchase #5	$11.61	5.871%	$12.2916	$12.29	$12.30	$12.30
Purchase #6	$168.33	7.343%	$180.6905	$180.69	$180.70	$180.70
Purchase #7	$173.38	8.736%	$188.5265	$188.53	$188.55	$188.50
7 purchase totals =	$780.67		$842.8312	$842.83	$842.90	$842.80