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	$102.53	9.834%	$112.6128	$112.61	$112.60	$112.60
Purchase #2	$127.73	10.685%	$141.378	$141.38	$141.40	$141.40
Purchase #3	$180.92	6.284%	$192.289	$192.29	$192.30	$192.30
Purchase #4	$126.26	8.518%	$137.0148	$137.01	$137.00	$137.00
Purchase #5	$137.46	10.145%	$151.4053	$151.41	$151.40	$151.40
Purchase #6	$96.31	10.815%	$106.7259	$106.73	$106.75	$106.70
Purchase #7	$88.64	13.542%	$100.6436	$100.64	$100.65	$100.60
7 purchase totals =	$859.85		$942.0694	$942.07	$942.10	$942.00