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	$191.84	4.275%	$200.0412	$200.04	$200.05	$200.00
Purchase #2	$46.98	6.451%	$50.0107	$50.01	$50.00	$50.00
Purchase #3	$129.31	8.860%	$140.7669	$140.77	$140.75	$140.80
Purchase #4	$245.59	10.663%	$271.7773	$271.78	$271.80	$271.80
Purchase #5	$142.74	7.767%	$153.8266	$153.83	$153.85	$153.80
Purchase #6	$250.56	4.277%	$261.2765	$261.28	$261.30	$261.30
Purchase #7	$92.83	12.868%	$104.7754	$104.78	$104.80	$104.80
7 purchase totals =	$1,099.85		$1,182.4746	$1,182.49	$1,182.55	$1,182.50