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	$129.97	9.355%	$142.1287	$142.13	$142.15	$142.10
Purchase #2	$179.84	11.488%	$200.5	$200.50	$200.50	$200.50
Purchase #3	$45.54	6.755%	$48.6162	$48.62	$48.60	$48.60
Purchase #4	$215.98	9.642%	$236.8048	$236.80	$236.80	$236.80
Purchase #5	$196.86	9.421%	$215.4062	$215.41	$215.40	$215.40
Purchase #6	$90.51	7.571%	$97.3625	$97.36	$97.35	$97.40
Purchase #7	$43.69	4.184%	$45.518	$45.52	$45.50	$45.50
7 purchase totals =	$902.39		$986.3364	$986.34	$986.30	$986.30