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	$86.94	8.269%	$94.1291	$94.13	$94.15	$94.10
Purchase #2	$243.42	6.554%	$259.3737	$259.37	$259.35	$259.40
Purchase #3	$151.58	12.375%	$170.338	$170.34	$170.35	$170.30
Purchase #4	$37.31	11.664%	$41.6618	$41.66	$41.65	$41.70
Purchase #5	$56.57	10.525%	$62.524	$62.52	$62.50	$62.50
Purchase #6	$178.32	3.107%	$183.8604	$183.86	$183.85	$183.90
Purchase #7	$181.50	4.353%	$189.4007	$189.40	$189.40	$189.40
7 purchase totals =	$935.64		$1,001.2877	$1,001.28	$1,001.25	$1,001.30