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	$42.56	8.205%	$46.052	$46.05	$46.05	$46.10
Purchase #2	$171.94	11.160%	$191.1285	$191.13	$191.15	$191.10
Purchase #3	$48.31	9.480%	$52.8898	$52.89	$52.90	$52.90
Purchase #4	$69.82	3.642%	$72.3628	$72.36	$72.35	$72.40
Purchase #5	$98.55	12.636%	$111.0028	$111.00	$111.00	$111.00
Purchase #6	$31.28	8.201%	$33.8453	$33.85	$33.85	$33.80
Purchase #7	$49.81	12.555%	$56.0636	$56.06	$56.05	$56.10
7 purchase totals =	$512.27		$563.3448	$563.34	$563.35	$563.40