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	$121.97	4.128%	$127.0049	$127.00	$127.00	$127.00
Purchase #2	$76.66	11.786%	$85.6951	$85.70	$85.70	$85.70
Purchase #3	$50.65	9.862%	$55.6451	$55.65	$55.65	$55.60
Purchase #4	$235.70	5.433%	$248.5056	$248.51	$248.50	$248.50
Purchase #5	$161.68	11.229%	$179.835	$179.84	$179.85	$179.80
Purchase #6	$156.78	9.402%	$171.5205	$171.52	$171.50	$171.50
Purchase #7	$56.38	7.407%	$60.5561	$60.56	$60.55	$60.60
7 purchase totals =	$859.82		$928.7623	$928.78	$928.75	$928.70