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	$233.65	4.203%	$243.4703	$243.47	$243.45	$243.50
Purchase #2	$181.72	12.261%	$204.0007	$204.00	$204.00	$204.00
Purchase #3	$75.52	3.484%	$78.1511	$78.15	$78.15	$78.20
Purchase #4	$81.29	6.354%	$86.4552	$86.46	$86.45	$86.50
Purchase #5	$105.79	6.289%	$112.4431	$112.44	$112.45	$112.40
Purchase #6	$183.52	6.782%	$195.9663	$195.97	$195.95	$196.00
Purchase #7	$228.83	6.834%	$244.4682	$244.47	$244.45	$244.50
7 purchase totals =	$1,090.32		$1,164.9549	$1,164.96	$1,164.90	$1,165.10