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	$163.28	9.405%	$178.6365	$178.64	$178.65	$178.60
Purchase #2	$148.52	11.699%	$165.8954	$165.90	$165.90	$165.90
Purchase #3	$236.28	8.281%	$255.8463	$255.85	$255.85	$255.80
Purchase #4	$43.95	5.865%	$46.5277	$46.53	$46.55	$46.50
Purchase #5	$241.75	10.561%	$267.2812	$267.28	$267.30	$267.30
Purchase #6	$51.72	6.585%	$55.1258	$55.13	$55.15	$55.10
Purchase #7	$46.35	11.711%	$51.778	$51.78	$51.80	$51.80
7 purchase totals =	$931.85		$1,021.0909	$1,021.11	$1,021.20	$1,021.00