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	$218.36	12.416%	$245.4716	$245.47	$245.45	$245.50
Purchase #2	$118.25	13.467%	$134.1747	$134.17	$134.15	$134.20
Purchase #3	$39.77	9.487%	$43.543	$43.54	$43.55	$43.50
Purchase #4	$215.30	3.861%	$223.6127	$223.61	$223.60	$223.60
Purchase #5	$39.44	11.148%	$43.8368	$43.84	$43.85	$43.80
Purchase #6	$188.92	10.368%	$208.5072	$208.51	$208.50	$208.50
Purchase #7	$96.29	7.411%	$103.4261	$103.43	$103.45	$103.40
7 purchase totals =	$916.33		$1,002.5721	$1,002.57	$1,002.55	$1,002.50