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	$120.39	6.154%	$127.7988	$127.80	$127.80	$127.80
Purchase #2	$138.41	9.687%	$151.8178	$151.82	$151.80	$151.80
Purchase #3	$191.84	6.498%	$204.3058	$204.31	$204.30	$204.30
Purchase #4	$200.89	10.212%	$221.4049	$221.40	$221.40	$221.40
Purchase #5	$51.63	7.821%	$55.668	$55.67	$55.65	$55.70
Purchase #6	$133.32	4.236%	$138.9674	$138.97	$138.95	$139.00
Purchase #7	$186.60	7.688%	$200.9458	$200.95	$200.95	$200.90
7 purchase totals =	$1,023.08		$1,100.9085	$1,100.92	$1,100.85	$1,100.90