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	$206.82	13.658%	$235.0675	$235.07	$235.05	$235.10
Purchase #2	$89.53	4.450%	$93.5141	$93.51	$93.50	$93.50
Purchase #3	$240.91	6.149%	$255.7236	$255.72	$255.70	$255.70
Purchase #4	$50.77	6.524%	$54.0822	$54.08	$54.10	$54.10
Purchase #5	$239.35	10.232%	$263.8403	$263.84	$263.85	$263.80
Purchase #6	$19.85	12.448%	$22.3209	$22.32	$22.30	$22.30
Purchase #7	$165.59	9.451%	$181.2399	$181.24	$181.25	$181.20
7 purchase totals =	$1,012.82		$1,105.7885	$1,105.78	$1,105.75	$1,105.70