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	$178.79	9.794%	$196.3007	$196.30	$196.30	$196.30
Purchase #2	$224.91	9.842%	$247.0456	$247.05	$247.05	$247.00
Purchase #3	$77.50	11.695%	$86.5636	$86.56	$86.55	$86.60
Purchase #4	$90.55	9.242%	$98.9186	$98.92	$98.90	$98.90
Purchase #5	$14.79	7.586%	$15.912	$15.91	$15.90	$15.90
Purchase #6	$197.80	3.419%	$204.5628	$204.56	$204.55	$204.60
Purchase #7	$137.57	9.687%	$150.8964	$150.90	$150.90	$150.90
7 purchase totals =	$921.91		$1,000.1997	$1,000.20	$1,000.15	$1,000.20