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	$220.32	3.589%	$228.2273	$228.23	$228.25	$228.20
Purchase #2	$80.52	13.744%	$91.5867	$91.59	$91.60	$91.60
Purchase #3	$126.41	11.428%	$140.8561	$140.86	$140.85	$140.90
Purchase #4	$119.28	7.123%	$127.7763	$127.78	$127.80	$127.80
Purchase #5	$45.46	13.738%	$51.7053	$51.71	$51.70	$51.70
Purchase #6	$182.97	12.375%	$205.6125	$205.61	$205.60	$205.60
Purchase #7	$160.30	13.132%	$181.3506	$181.35	$181.35	$181.40
7 purchase totals =	$935.26		$1,027.1148	$1,027.13	$1,027.15	$1,027.20