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	$242.57	7.259%	$260.1782	$260.18	$260.20	$260.20
Purchase #2	$218.55	11.872%	$244.4963	$244.50	$244.50	$244.50
Purchase #3	$68.83	13.462%	$78.0959	$78.10	$78.10	$78.10
Purchase #4	$123.46	3.379%	$127.6317	$127.63	$127.65	$127.60
Purchase #5	$208.57	9.474%	$228.3299	$228.33	$228.35	$228.30
Purchase #6	$85.56	12.676%	$96.4056	$96.41	$96.40	$96.40
Purchase #7	$46.68	4.819%	$48.9295	$48.93	$48.95	$48.90
7 purchase totals =	$994.22		$1,084.0671	$1,084.08	$1,084.15	$1,084.00