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	$221.25	4.426%	$231.0425	$231.04	$231.05	$231.00
Purchase #2	$84.76	8.628%	$92.0731	$92.07	$92.05	$92.10
Purchase #3	$136.80	13.510%	$155.2817	$155.28	$155.30	$155.30
Purchase #4	$97.36	5.837%	$103.0429	$103.04	$103.05	$103.00
Purchase #5	$181.71	5.560%	$191.8131	$191.81	$191.80	$191.80
Purchase #6	$136.82	5.474%	$144.3095	$144.31	$144.30	$144.30
Purchase #7	$87.66	12.676%	$98.7718	$98.77	$98.75	$98.80
7 purchase totals =	$946.36		$1,016.3346	$1,016.32	$1,016.30	$1,016.30