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	$124.68	5.299%	$131.2868	$131.29	$131.30	$131.30
Purchase #2	$134.75	3.700%	$139.7358	$139.74	$139.75	$139.70
Purchase #3	$120.79	12.791%	$136.2402	$136.24	$136.25	$136.20
Purchase #4	$51.76	11.862%	$57.8998	$57.90	$57.90	$57.90
Purchase #5	$167.55	5.288%	$176.41	$176.41	$176.40	$176.40
Purchase #6	$228.46	11.687%	$255.1601	$255.16	$255.15	$255.20
Purchase #7	$167.84	6.674%	$179.0416	$179.04	$179.05	$179.00
7 purchase totals =	$995.83		$1,075.7743	$1,075.78	$1,075.80	$1,075.70