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	$142.99	6.695%	$152.5632	$152.56	$152.55	$152.60
Purchase #2	$49.67	6.376%	$52.837	$52.84	$52.85	$52.80
Purchase #3	$104.40	10.316%	$115.1699	$115.17	$115.15	$115.20
Purchase #4	$240.52	8.461%	$260.8704	$260.87	$260.85	$260.90
Purchase #5	$198.77	12.482%	$223.5805	$223.58	$223.60	$223.60
Purchase #6	$18.96	7.183%	$20.3219	$20.32	$20.30	$20.30
Purchase #7	$171.54	6.367%	$182.462	$182.46	$182.45	$182.50
7 purchase totals =	$926.85		$1,007.8049	$1,007.80	$1,007.75	$1,007.90