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	$42.49	10.134%	$46.7959	$46.80	$46.80	$46.80
Purchase #2	$171.40	6.167%	$181.9702	$181.97	$181.95	$182.00
Purchase #3	$137.69	5.769%	$145.6333	$145.63	$145.65	$145.60
Purchase #4	$229.42	4.676%	$240.1477	$240.15	$240.15	$240.10
Purchase #5	$56.56	10.493%	$62.4948	$62.49	$62.50	$62.50
Purchase #6	$191.84	8.623%	$208.3824	$208.38	$208.40	$208.40
Purchase #7	$111.46	8.109%	$120.4983	$120.50	$120.50	$120.50
7 purchase totals =	$940.86		$1,005.9226	$1,005.92	$1,005.95	$1,005.90