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	$154.64	6.306%	$164.3916	$164.39	$164.40	$164.40
Purchase #2	$168.76	11.617%	$188.3648	$188.36	$188.35	$188.40
Purchase #3	$19.96	11.783%	$22.3119	$22.31	$22.30	$22.30
Purchase #4	$48.89	11.159%	$54.3456	$54.35	$54.35	$54.30
Purchase #5	$250.94	5.240%	$264.0893	$264.09	$264.10	$264.10
Purchase #6	$69.75	4.414%	$72.8288	$72.83	$72.85	$72.80
Purchase #7	$234.51	6.737%	$250.3089	$250.31	$250.30	$250.30
7 purchase totals =	$947.45		$1,016.6409	$1,016.64	$1,016.65	$1,016.60