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	$171.69	9.288%	$187.6366	$187.64	$187.65	$187.60
Purchase #2	$215.75	4.482%	$225.4199	$225.42	$225.40	$225.40
Purchase #3	$217.68	4.637%	$227.7738	$227.77	$227.75	$227.80
Purchase #4	$101.32	9.374%	$110.8177	$110.82	$110.80	$110.80
Purchase #5	$212.77	4.550%	$222.451	$222.45	$222.45	$222.50
Purchase #6	$98.84	11.104%	$109.8152	$109.82	$109.80	$109.80
Purchase #7	$140.90	7.536%	$151.5182	$151.52	$151.50	$151.50
7 purchase totals =	$1,158.95		$1,235.4324	$1,235.44	$1,235.35	$1,235.40