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	$41.36	3.740%	$42.9069	$42.91	$42.90	$42.90
Purchase #2	$173.45	5.310%	$182.6602	$182.66	$182.65	$182.70
Purchase #3	$126.62	4.113%	$131.8279	$131.83	$131.85	$131.80
Purchase #4	$33.30	3.347%	$34.4146	$34.41	$34.40	$34.40
Purchase #5	$248.66	7.710%	$267.8317	$267.83	$267.85	$267.80
Purchase #6	$215.62	11.365%	$240.1252	$240.13	$240.15	$240.10
Purchase #7	$7.45	6.379%	$7.9252	$7.93	$7.95	$7.90
7 purchase totals =	$846.46		$907.6917	$907.70	$907.75	$907.60